What happens when a plane runs out of fuel, including how long it can glide for

Telegraph

10-03-2025

It recently emerged that a Tui plane came within 20 minutes of running out of fuel. What would have happened, if it had?
In December 2023, the Boeing 737, carrying 300 passengers, was forced to declare a mayday emergency during Storm Gerrit when its fuel reserves dropped below the legal limits.
The Tui aircraft, which took off from Cancún in Mexico, was due to land at Manchester Airport but after encountering gusts of up to 53mph was diverted to East Midlands Airport.
It was then forced to make a second diversion to Birmingham Airport, where it joined a queue of seven planes waiting to land. A report published in mid-February by the AAIB found that by the time it landed, it only had 1.2 tonnes of kerosene in the tank, below the legal minimum of 1.9 tonnes.
Brian Smith, a commercial pilot with decades of experience flying Boeing planes, says this scenario is one of every pilot's worst nightmares.
'Apart from some murderous hijacker or terrorist, only three things will create a lasting adrenalin rush in the cockpit: a fire that will not extinguish in the cabin or hold, being uncertain of position in bad weather near terrain, or, indeed, running out of fuel.'
Here, Smith reveals how pilots prepare for this eventuality, and the steps they take if the fuel tank runs dangerously close to empty.
How much extra fuel do planes have on board?
'Airlines issue flight crew with a comprehensive 'Flight Plan' for the journey. It is very detailed and as a bare minimum includes the route, weights of the aircraft and payload, and weather at destination and along the route.
'Crucially, it also shows how much fuel will be needed for the flight. However, it is the commander's responsibility to ensure sufficient fuel is loaded for all conceivable contingencies.
'The fuel plan consists of four stages: Taxi, Trip, Contingency (typically 5 per cent of the trip), and Alternate fuels. A fully loaded 747 Jumbo could have as much as 170 tons of fuel on board. The figures are generally extremely accurate. The commander has discretion to add fuel as he sees fit, according to weather conditions and perhaps some issue at an airport that could cause a delay, like the arrival of VIPs, for example.
'In a majority of cases, contingency will cover any small additional fuel burn, but bad weather forecasts should result in the commander carrying more fuel, just in case.'
When do pilots rely on their final fuel reserves?
'Alternate fuel, required to fly a missed approach and divert to the selected alternate airport, includes 'Final Reserve'; an amount sufficient to fly above an airport for 30 minutes at about 1,500 feet. This amount of fuel is critical and when fuel quantity is approaching it, things get very tense.'