How High Do Planes Fly?
What is the typical cruise altitude of a passenger jet?
How High do Passenger Planes Fly?
Most commercial passenger jets typically cruise at an altitude of 30,000 to 42,000 feet. This is between 5 to 7 miles up in the sky or 8 to 11 kilometres (8,000 to 11,000 meters). Aircraft cruise at this high altitude due to enhanced fuel efficiency when compared to lower levels.
Flight Levels for Aircraft
In most countries around the world, when at high altitude, the aircraft’s height is reported as a ‘Flight Level’ in feet. The reported flight level is the current altitude of the aircraft but with two of the zeros removed for the end. For example, 36,000 feet is reported as Flight Level 360 (FL360).
China still requires aircraft to report their height in meters rather than feet.
Even vs Odd Flight Levels
In the majority of airspace around the world, if an aircraft is travelling Eastbound (heading 360 – 179 degrees) they must fly at an odd flight level (e.g. FL330). An aircraft heading Westbound (180 – 359 degrees) must fly at an even flight level (e.g. FL380). Exceptions to this include specific airways and the airspace over the North Atlantic.
How High Did Concorde Fly?
Concorde still holds the record for the highest commercial passenger aircraft cruise altitude. Because of its unique design and powerful engines, Concorde was able to cruise at about 60,000 feet or 18,000 meters (10 miles up). Despite Concorde being retired in 2003, current commercial passenger jets still can’t get anywhere near this cruising altitude.
How High do Light Aircraft Fly?
Small, unpressurised, light propeller aircraft typically fly up to about 10,000 feet. Smaller aircraft like a Cessna 152 or PA-28 are limited in their maximum altitude due to the limitations of their piston engines and the oxygen requirements above this altitude.
However, some supercharged single engine piston aircraft, like the SR22, can reach altitudes of up to 25,000.
How High do Military Aircraft Fly?
Advanced military fighter jets like the F22 Raptor, F35 Lightning or the Eurofighter Typhoon can reach altitudes of between 50,000 – 65,000ft.
How High can Business Jet Fly?
Some business jet aircraft such as the Global 6000, the Falcon 5X and the Gulfstream G650 can reach altitudes of 51,000 feet. This is about 10,000 feet higher than the maximum cruising altitude of most commercial passenger planes.
What is the Highest Altitude a Plane has Ever Reached?
The highest altitude ever recorded by an aircraft with an ‘air breathing’ engine is the SR-71 Blackbird which could reach approximately 90,000 feet. Rocket propelled aircraft can travel higher but these are not considered aircraft in this sense.
Why do Planes Abort Landings?
An aborted landing (which is known as a ‘go-around’ by pilots), can happen for a number of reasons such as bad weather, a blocked runway or an unstabilised approach. Go-arounds are very safe manoeuvres which are regularly practiced by pilots in the simulator. Go-arounds or aborted landings are fairly rare and occur around 1 to 3 times in every 1,000 approaches.
Aborted landings can be referred to using a number of terms. Passengers and the media often use generic terms to describe the aircraft going back up into the air after being established on final approach which covers a range of scenarios. However, technically, there are different types of ‘go-arounds’ depending on at which point the manoeuvre occurs.
Go-around – this is official the term used by pilots to describe the manoeuvre of discontinuing the approach and taking the aircraft back up into the air before making another attempt.
Rejected Landing – The definition of a ‘rejected landing’ slightly differs from a go-around. A rejected landing occurs if the decision is made to reject the landing after the pilots have commenced the ‘flare’. The flare is the point at which the pilots raise the nose of the aircraft at approximately 30ft above the runway to reduce the aircraft’s rate of descent and (hopefully!) get a smooth landing. On some aircraft types, the initial rejected landing procedure differs slightly from the go-around procedures.
Baulked Landing – This is the same as a ‘rejected landing’. It occurs once the flare has commenced and may result in the aircraft’s main landing gear touching the runway before going around.
Aborted Landing – This isn’t a term typically used by pilots, but could be used to refer to either a go-around or a rejected landing.
Discontinued Approach – This is a term sometimes used by the pilots when explaining to the passengers what has happened in the subsequent PA after a go-around has been flown. The term ‘Discontinued Approach’ is considered to be more relatable, understandable and less scary for passengers than ‘go-around’ or ‘aborted landing’.
Touch & Go – This is a planned manoeuvre, typically flown as part of pilot training. During a touch and go, the aircraft will land on the runway (or ‘touch down’) and then take off straight away again without stopping. The difference between this and a rejected landing is that a touch and go is a planned manoeuvre, a rejected landing is not.
What Causes a Plane to Go-Around?
There can be many reasons which would cause an aircraft to go-around which happens many times every day across the world. These are some of the more common reasons, although a go-around can be caused by just about anything.
Air Traffic Control – On occasions, an aircraft may be told to go-around by ATC. This might happen if the spacing between two aircraft landing has become too close. It may also occur if another aircraft gets stuck on the runway due to a technical malfunction or a problem that needs resolving.
Weather – Challenging weather conditions might cause the aircraft to go-around. Some examples include:
- A sudden change in the speed or direction of wind.
- Strong winds. Aircraft have maximum wind limitations. Wind strength outside these parameters might require the aircraft to go-around. This includes a strong tailwind (usually more than about 15kts) or a very strong cross-wind (normally more than 35-40kts).
- Cloud base. Depending on the aircraft, airport and type of approach, the pilots need to see the runway by a certain altitude. If at a certain altitude (200ft for example), the pilots are unable to see the runway, they must discontinue the approach.
- Different runways have differing minimum visibility requirements for landing. Fog, mist, smoke, dust storms, snow and rain can all reduce visibility to below the minimum required for landing.
Unstabilised – Most airlines require the aircraft to be ‘stabilised’ by a certain altitude (typically either 1,000ft or 500ft). If the aircraft is unstabilised, or becomes unstabilised below this altitude, a go-around must be flown. Stabilised refers to the following parameters being met:
- Aircraft in the landing configuration (landing gear down and landing flap set)
- At the correct target speed for landing
- Landing checklist complete
- The aircraft is on the correct vertical profile for the approach being flown (typically a 3-degree descent angle and descending at about 700-800 feet per minute)
- The aircraft is on the correct lateral profile
So, if an aircraft is too high, low, fast etc., then the approach should be discontinued.
Technical Problem – If a technical problem occurs onboard the aircraft during final approach, particularly one that might affect the stopping distance of the aircraft, the pilots may elect to go-around to resolve the problem and/or recalculate the landing distance required.
Deep Landing – The aircraft must touch down within the ‘touch down zone’ which is marked out on the runway. If it looks like the aircraft will miss the touchdown zone, a rejected landing should be flown.
What is the V1 Speed for a Commercial Aircraft?
V1 has two different meanings. Firstly, it is the speed by which the first action must have been taken to reject the take-off if the aircraft is to safely stop on the remaining runway. Secondly, V1 is also the minimum speed at which the aircraft is ‘guaranteed’ to get airborne and reach the screen height (35ft dry and 15ft wet) in the remaining take-off distance available if an engine fails.
The FAA state taking the first action to stop the aircraft can be:
- Reducing thrust
- Applying the brakes
- Deploying the speedbrake
In summary, if an engine fails below V1 and the take-off is continued, the aircraft may not get airborne in the remaining take-off distance available. If a take-off is rejected above V1, the aircraft may not be able to stop on the remaining runway available (technically accelerate-stop distance available or ASDA) and leave the paved surface.
The Decision Speed on Take-off?
V1 has previously been called the ‘Go / No-go’ or a ‘decision’ speed, but these are no longer considered to be the most appropriate phrases. This is because the first action to reject the take-off must have been taken by V1 and therefore the decision as to whether to go or stop should have been made prior to V1. Whilst it should not be considered, there is a 2 second buffer built into the calculations which would allow the pilots to reject the take-off 2-seconds after V1 and still be able to stop on the remaining runway. This is an additional safety margin.
V1 must always be greater than VMCG and less than VR.
What affects V1?
V1 is calculated by the pilots prior to every flight. V1 is affected by:
- Take-off Distance Available
- Flap Setting
- Pressure Altitude (Temperature, Pressure, Field Elevation)
- Aircraft Weight
- Runway Surface State (i.e. dry, wet, contaminated)
- Runway Slope
- Wind Speed and Direction
Since V1 must be more than VMCG and less than VR, these speeds can also affect the V1 speed (and therefore the variables which affect these speeds such as engine thrust).
What is the normal V1 speed for a commercial jet?
What happens at V1 on the flight deck?
The pilot monitoring (i.e. the pilot who is not flying the aircraft but is monitoring the instruments) usually calls out V1. On some jets this is automatically called out by the flight computers. When V1 is called out, the pilot flying, or at some airlines the Captain, removes their hands from the thrust levers to stop them reducing the thrust and rejecting the take-off if a malfunction occurs.
Can Planes Reverse?
A look at if planes can reverse in the air and on the ground…
Can Planes Reverse?
Whilst all commercial passenger aircraft can theoretically reverse on the ground using reverse thrust, practically speaking, only a very limited number of small commuter aircraft do reverse on the ground. They do this when leaving the gate to ‘push themselves back’ rather than having to rely on a tug to do it. This saves time and reliance on ground services which might not always be available at smaller airports. Aircraft that reverse themselves are all propeller aircraft, no passenger jet aircraft would reverse itself.
Can Planes Reverse in the Air?
No commercial passenger plane can reverse in the air and the pilots can’t intentionally deploy reverse thrust in flight in any modern passenger jet aircraft. Reverse thrust is ‘locked out’ until the aircraft senses its wheels are on the ground.
A small number of military aircraft are able to manoeuvre their thrust output vector which allows them to either hover or reverse whilst flying. Military aircraft that can reverse whilst flying include the Lockheed Martin F-35 Lightning II and the Harrier Jump Jet.
Some military transport aircraft can also deploy reverse thrust in flight, but this just serves to increase the rate of descent. They might do this if they need to make a tactical approach where the aircraft must remain very high before rapidly descending towards the runway in order to avoid enemy fire. Despite reverse thrust being deployed, the aircraft is moving forwards at all times.
A Lockheed Martin F-35 Lightning II hovering in flight using its thrust vectoring technology.
Why can’t passenger jets reverse in the air?
In order to keep flying, an aircraft’s wing needs to have air flowing over it. To ensure air is always flowing over the wing, the plane must be flying at a minimum speed. If it goes too slowly, not enough air is flowing over the wing and this will cause a stall. Therefore, the plane must always be moving forward to keep flying.
As highlighted above, a very small number of military aircraft, can manoeuvre their engines to direct the thrust output downwards instead of backwards. In these aircraft, the downward thrust vector is so powerful that it can support the aircraft weight without air flowing over the wing which allows it to hover or reverse (very slowly).
Why don’t jet aircraft reverse on the ground?
Large passenger aircraft reversing under their own power on the ground is dangerous for a number of reasons. These include:
You can’t see! Commercial aircraft can be very big and take up a lot of space. Pushing the plane back from the gate is a skilful manoeuvre given there are often lots of other aircraft and equipment in close vicinity. It requires a number of people to keep a good look out and make sure the area is clear. Therefore, a tug is used which allows a high degree of manoeuvrability and precision, something you wouldn’t get when using reverse thrust. If the pilots were to do this themselves using the engine reverse thrust, they wouldn’t be able to see where they were going and would almost certainly end up hitting something.
High power required. Generating enough power to reverse the aircraft takes a considerable amount of thrust. Applying high thrust settings on the ground anywhere other than the runway or in dedicated engine runup area (for maintenance purposes) can cause considerable damage to airport infrastructure, other aircraft and people.
Lack of control and manoeuvrability. Attempting to steer a 300-tonne aircraft whilst reversing under its own power using the nose wheel is very difficult.
If you thought this was an interesting article, have a read of our page on ‘Can a plane fly with only 1 engine‘.
What Happens if a Passenger Plane Flies Too High?
A look at what happens if a commercial passenger jet flies too high…
If a passenger jet flies too high, it reaches a point called ‘Coffin Corner’. This is the point at which the aircraft’s low speed stall and high-speed buffet meet and the plane can no longer maintain its altitude which forces it to descend. For a regular passenger jet this occurs at a height of around 40,000ft – 45,000ft, but it can be higher or lower depending on the aircraft’s weight and environmental conditions.
A low speed stall is where there is not enough air passing over the wing to keep the aircraft flying and high-speed buffet is where the air over the wing is going fast enough to cause a shockwave which can result in aircraft control issues. At the altitude at which Coffin Corner occurs, the plane can’t speed up, slow down or climb; the only way to keep the aircraft flying safely is to reduce the altitude and go down. Pilots are aware of what the maximum altitude is and ensure they do not reach it.
What limits a plane’s altitude?
The maximum altitude of a passenger aircraft is limited by 3 factors and any one of these factors can be the limiting one on any given day depending on air temperature and aircraft weight.
The air at high altitude is very thin (less dense). It gets so thin that at a certain altitude not enough air can pass through the engine for it produce enough thrust to keep the aircraft climbing. The density of the air is dictated by the temperature. So, on hot days, the aircraft’s maximum altitude is lower than on cold days. The engine limited altitude is said to be the altitude at which the aircraft can no longer achieve a rate of climb of at least 300 feet per minute.
Cabin Pressure Differential
As the air at high altitude is so thin, it doesn’t contain enough oxygen for a person to survive if they had to breathe it in. It’s also very cold reaching temperatures as low as -60c. Therefore, compressed heated air is supplied by the engines (before it’s mixed with fuel) to the aircraft cabin. By forcing air into the cabin, it increases the air pressure and allows passengers to breath normally.
This creates a difference in pressure between inside the cabin and outside environment which is contained by the aircraft fuselage. The higher the aircraft flies, the higher this pressure difference becomes. The maximum pressure differential between the inside of the aircraft and outside is about 9 PSI. This limit is reached when the aircraft reaches around 43,000ft. If the aircraft flew any higher, the maximum pressure differential could be exceeded and this could cause structural failure of the fuselage.
Coffin Corner / Aerodynamic Altitude
A margin of safety is applied to ensure coffin corner is never reached. Typically, a 1.3g margin is used to determine the aircraft’s maximum aerodynamic altitude. This altitude varies with the weight of the aircraft.
Your pilots are aware of which altitude is limiting on any given day and will ensure the aircraft is operated within these limits. Pilots are also given extensive training on how to recover from an event where any of the above issues occur.
How Fast Do Passenger Jets Fly?
Just how quickly do passenger aircraft fly?
How fast do commercial passenger jets fly?
A typical commercial passenger jet flies at a speed of about 400 – 500 knots which is around 460 – 575 mph when cruising at about 36,000ft. This is about Mach 0.75 – 0.85 or in other words, about 75-85% of the speed of sound. Generally speaking, the higher the aircraft flies, the faster it can travel.
This high speed can only be achieved at high altitude, which is one of the reasons why commercial aircraft fly so high.
Different Types of Speed Measurements
Speed can get a bit confusing when talking about an object moving through the air. You have a few types of speed; airspeed (and there a quite a lot of variations of airspeed) and ground speed.
What is Ground Speed?
Ground speed is the time it takes you to cover a certain distance over the ground. For example, when at cruise altitude, aeroplanes might have a ground speed anywhere between 300 – 600 nautical miles per hour.
Whilst passenger jets usually cruise at roughly the same airspeed, the wind can make a big difference to the speed at which the aircraft passes over the ground.
A tailwind pushes the aircraft along at a faster speed whilst a headwind slows the aircraft’s speed across the ground down down.
When a strong tailwind occurs, such as when crossing the Atlantic from West to East, the aircraft’s ground speed might reach exceed over 700mph.
Airspeed has a few different variations. If an aircraft is sat still on the runway and has a 20 mph headwind, the aircraft already has an airspeed of 20 mph, despite the fact it isn’t actually moving. This is because airspeed is a measure of the speed of the air over the wing. The speed of the air travelling over the wing dictates how much lift the wing is producing, and it’s this lift that allows the aircraft to support its own weight and allows it to fly.
If an aircraft has a take off speed of 140 mph, but has a 20 mph headwind, the aircraft will only need to achieve a 120 mph ground speed before it is able to take off. Conversely, if an aircraft has a 20 mph tail wind, it would need to achieve a 160 mph ground speed in order to lift off the ground.
Pilots always make reference their airspeed rather than ground speed as it is the airspeed that keeps the aircraft flying. The groundspeed is a byproduct. In principle, if you had about a 140 mph headwind the aircraft could lift off the ground without moving forward!
The Speed of Sound
When aircraft get to between 25,000 – 30,000 ft, they reference their speed to a “Mach Number” rather than knots. This is simply a percentage of the speed of sound. For example, a Mach Number of 0.80 is 80% of the speed of sound. This is not a fixed speed, as the speed of sound varies with the temperature of the air.
The speed of sound at sea level with an air temperature of 15 degrees celsius is 761 Miles Per Hours. This reduces to about 660 miles an hour at -57 degrees celsius when at 36,000ft.
When aircraft approach the speed of sound, shockwaves start to form which causes aerodynamic issues. Aircraft therefore have a maximum mach number they can fly at, which is why this becomes the reference speed.
How Much Does Jet Fuel Cost?
As of January 2022, the price of Jet A1 was approximately $816 per metric tonne. With a metric tonne being 1,000 KG or 2,204 lbs, this equates to about $0.82 / £0.61 per KG.
This price is around double what was around one year ago (January 2021) where the price of Jet A1 was approximately $430 per metric tonne or about $0.43 per KG.
Due to collapse in oil price bought about by the Covid-19 pandemic, at one point (May 2020), Jet A1 was as low as $200 per metric tonne which equates to around $0.20 per KG.
1 KG (kilograms) = 2.2 LBS (pounds)
1 MT (metric tonne) = 1,000 KGS
The price of jet fuel (known as Jet A1) is closely aligned the price of oil which varies on a daily basis. As an example, in May 2020, the price of Jet A1 was down 69% compared to the previous 12 months.
Example Jet Fuel Cost Calculations
The price of jet fuel as of January 2022 is as follows:
- $2.46 (US dollars) per Gallon
- 1 litre = 0.65 pence (pound sterling)
- 1 litre = 0.78 Euros
It should be noted that it does not include the delivery of the fuel or the fee to actually refuel the aircraft. Therefore, the price airlines actually pay for the fuel per kilogram will be higher than the figures outlined above, subject to the contract details. At present there is no tax on aviation fuel in the UK or Europe.
A Jumbo Jet (Boeing 747-400) flying from London to New York burns approximately 70,000 kilograms of fuel. As jet fuel has an approximate specific gravity of 0.85 (the measure of its density), this therefore equates to 82,300 litres.
Based on these figures, the cost of the fuel required to fly from London to New York being operated by a B747 Jumbo Jet is approximately £53,500 (€64,300), which based on 450 passengers, would work out at £118 (€141 / $158) per person.
Fuel Price Hedging
The prices airlines actually pay for their fuel varies substantially depending on what price they’ve “hedged” the fuel at. Hedging is where you agree a constant price for fuel for a set period of time into the future. This helps an airline to reduce risk and fixed costs which can be important for financial planning. For example, a fixed amount of fuel, lets say 5 million tonnes, might be hedged at $600 per metric tonne for 12 months. The airline will pay $600 per metric tonne regardless of any fluctuation in price of fuel during this time. If the fuel price goes up, the airline is protected from this rise whilst if there is a drop in fuel price, the airline will be paying more for fuel than it might have done.
The hedging is normally based on purchasing a set quantity of fuel. If the airline stops flying, such as due to the COVID-19 crisis and don’t use the fuel they’ve hedged, the airlines still have to pay for the fuel they hedged even if they don’t use it which can result in financial loses.
How much does it cost to fully fuel an A380?
The A380 can hold approximately 315,000 litres of fuel. It would therefore cost approximately £205,000 to fill an A380 full of fuel.
Why Would Both Engines Fail On A Commercial Passenger Jet?
A look at the reasons that a passenger aircraft’s engines might fail . . .
What could cause a double engine failure on a passenger jet?
Any engine failure on a passenger jet is a very rare occurrence, and a double engine failure is extremely improbable. But is has happened. Both bird strikes, and fuel starvation could cause both engines to shut down. If a plane loses all its engines at a typical crusing altitude of 36,000, it could still glide for up to 60 miles. Here are some of the factors which have caused double engine failures in the past.
Birds can be very hazardous to aircraft. Flying through a flock of geese caused both engines to fail on US Airways Flight 1549 in 2009 that subsequently landed in the Hudson river in New York. A similar incident occurred in 2008 when Ryanair flight 4102 suffered around 90 individual bird strikes when flying through a flock of starlings on final approach into Rome Ciampino airport. Despite losing both the 737’s engines, the crew managed to land the aircraft on the runway. The aircraft was written off. There is a little a pilot can do to avoid birds other than try to manoeuvre the aircraft around them, but they often seen to late to attempt this.
Shutting down the wrong engine
It sounds difficult to believe, but it has happened. When there has been a problem with an engine, there have been examples of the crew shutting down the wrong engine as a result, leaving both engines failed. It’s not actually that difficult to do, especially when factoring in all the stresses and information sources. A famous example of this was the British Midland Flight 92 crash at Kegworth where 47 people died. Airlines have updated their procedures as a result and the engine shutdown process is now carefully monitored by both pilots.
A fuel leak, or running out of fuel will cause both engines to fail. Air Transat 236 ran out of fuel due to a leak approximately 65 miles from the Azores in 2001. The pilots successfully managed to glide the aircraft to an airbase on the island. In 1983 Air Canda Flight 143 also ran out of fuel when descending through 35,000 feet, due to a fuel miscalculation (the weight of the fuel was measure in pounds instead of kilograms). The pilots successfully managed to glide the aircraft to safety onto a closed runway.
Icing in the fuel tanks could stop the engines from receiving fuel. This happened to flight BA38 in 2008 when ice in the fuel lines caused a dual engine flame out on final approach into London Heathrow. This was found to have been caused due to a an issue with the Boeing 777 fuel system. The quick actions of the Captain in making the decision to retract some of the flaps reduced the drag of aircraft which saved everyone on board.
This is where the ignition of the fuel stops. This could occur in extreme turbulence or very heavy rain / precipitation.
This can damage the engines to the point that they flame out or stops the combustion process. In 1982, British Airways flight 9, a Boeing 747, lost all four of its engines due to ingesting volcanic ash. The aircraft glided outside of the ash cloud and managed to restart its engines before successfully landing in Jakarta.
Believe it or not, there is a checklist on commercial aircraft for entire separation of the engine from the wing. The engine is held onto the wing by a ‘sheer pin’ to ensure the engine separates from the aircraft and protect the aircraft structure in the results of the engine suffering a significant impact.
What speed does a Boeing 777 take off and land at?
The Boeing 777-200ER take off or rotate speed (VR) typically occurs between 130 – 160 knots (roughly 120-180 mph) depending on the weight of the aircraft. At a typical take-off weight of around 230,000 kgs, the take off speed would be approximately 145 kts which is approximately 165 mph.
B777 Landing Speed
A typical landing speed (or speed over the threshold known as VREF) at a landing weight of 190,000 KGS is approximately 135 kts or 155 mph.
To converts nautical miles per hours (knots or kts) to miles per hour (mph), multiply the knots by 1.15.
What effects Take-off and Landing Speed for a passenger jet?
The speed at which aircraft take-off and land depends on a number of variables. These include aircraft weight, air temperature, airfield altitude and pressure.
The flap setting will also influence these speeds with a larger flap setting reducing take-off and landing speed. Factors such as runway length, climb performance and weight influence the decision of what flap setting to use for take-off and landing.
Check out our article on what speed the B747 Jumbo Jet takes off and lands at.
How Much Fuel are Aircraft Required to Carry?
How do you know you’ve got enough?
How Much Fuel are Passenger Jets Required to Carry?
The minimum amount of fuel which a passenger jet must carry is set out by regulators such as EASA and the FAA. Airlines are actually required to carry substantially more fuel for a flight than is required to get from A to B in case anything unexpected happens such as an airport closure or aircraft emergency. Commercial flights typically carry at least one hour’s worth of additional fuel on top of that required to get to their destination, but this is often increased by the pilots depending on the circumstances on the day.
Airlines must comply with the regulatory stipulations regarding carrying fuel. Most authorities policies are broadly similar and are detailed in each airline’s operating manuals.
Under EASA regulations (although FAA and other authorities are very similar) the Captain must ensure he has the following minimum fuel before departure:
- Trip Fuel
- Diversion fuel or 15 mins holding fuel if flight is planned with no alternate
- Reserve Fuel
- Contingency Fuel
- Taxi Fuel
- Additional Fuel
Fuel required from the start of take-off, through climb, cruise, descent and approach to touchdown at destination, assuming departure on the SID from the assumed runway and arrival using the STAR for the assumed arrival runway and routing based on the forecast wind.
Fuel required from go-around at destination, climb, cruise, descent, approach and landing at the selected alternate airport. This is normally calculated at the planned landing weight minus contingency fuel.
If no alternate is planned for the flight then the diversion fuel figure must be replaced by 15 mins holding fuel at 1500ft above destination airfield in standard conditions.
Is the minimum fuel required to be present in tanks at the alternate airfield (or destination if no planned alternate). The figure is calculated based on 30 mins of fuel holding at 1500ft in clean configuration at planned landing weight.
This is carried to cover unforeseen variations from the planned operation. For example different winds / temps from forecast or ATC restrictions on levels and speed. It can be used anytime after dispatch (once aircraft moves under its own power). It cannot be planned to use before. More likely it is used for delays on departure or arrival.
Contingency Fuel should be the higher of (i) or (ii) below:
a. Not less than 5% of the TRIP FUEL required from departure to destination; or
b. If an En-route alternate is available and selected, not less than 3% of the TRIP FUEL required from departure to destination; or
c. An amount of fuel sufficient for 20 minutes flying time based upon the planned trip fuel consumption; or
d. Statistical Contingency Fuel (SCF).
ii. An amount to fly for 5 minutes at holding speed at 1500 ft clean at Planned Landing Weight.
The minimum contingency fuel to be carried must not be below 5 minutes at holding speed at 1500 ft clean at Planned Landing Weight, even for the purpose of an LMC fuel reduction
This is fuel for APU burn on the ground, engine start and taxi out. Most airlines use statistical data to calculate this by using the taxi time in minutes.
Additional fuel is planned and loaded if the existing total fuel is not sufficient to cater for an engine failure (2 engines in 4 engine aircraft) or de-pressurisation at the most critical point along the route. Fuel planning must allow a descent and trip Fuel to alternate airfield, hold for 15 mins at 1500ft and make an approach and land.
Most airlines will work the total fuel required, which is presented to the pilots, through their flight planning system. The pilots will then make a decision as to whether they require any ‘extra’ fuel. There could be many reasons for requested additional fuel such as weather, ATC delays, an increase in passenger numbers or a technical defect.
The final decision as to how much fuel should be carried for a flight is always the responsibility of the Captain of the aircraft. The Captain will discuss the requirements to take any extra fuel with the First Officer prior to the flight commencing.