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

Yahoo

10-03-2025

It recently emerged that 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.
'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.'
'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.'
'Pilots are actually forbidden to land with less than Final Reserve, except in the most extreme of cases. If they anticipate landing with less than Final Reserve, the crew must declare 'MAYDAY FUEL' to receive immediate priority to land.'
'Aircraft have run out of fuel, but thankfully only rarely. The two most infamous cases are the 'Gimli Glider' – Air Canada 143, in July 1983 – and the 'Azores Glider' – Air Transat 236, which occurred in August 2001.
'The first was caused by human error during the refuelling, combined with some technical faults and poor company procedures, resulting in only 45 per cent of the required fuel load being carried. The captain, an experienced glider pilot, landed the 767 on a disused runway, on a former Air Force Base, then being used as a race track.
'Air Transat 236 ran out of fuel over the Atlantic due to a mishandled fuel leak following the fitting of an incorrect part to the hydraulic system. The Captain, also experienced in gliding, landed at Lajes, in the Azores. In both cases, all on board survived.'
'Since the engines cannot be restarted in these cases, the only option is to immediately turn towards a suitable runway or strip of concrete, and plan the ensuing glide.'
'Inside the cabin the noise of the engines would have stopped and it would become eerily quiet.
'The engines no longer generate any electrical power, so the lights may go out or dim. Flight instruments will, in most cases, be reduced to the captain's side only, and only be available for a limited time, typically 30 minutes.'
'An airliner can glide for about 100 miles from cruise altitude, which should offer a choice of airports unless over the ocean or wilderness.
'Big aircraft actually glide rather well, considering, and we do practice it in the simulator. The outcome is generally very good.'
'I'm pleased to say I've never encountered a fuel emergency: they tend to be more likely when weather conditions are deteriorating rapidly over a wide area, forcing multiple aircraft to divert at the same time, and when airports are closing or reaching capacity. It's worth pointing out just how good Air Traffic Control usually is in these cases, especially in the UK.'
'Airlines go to great lengths to train us to handle emergencies and to develop personal resilience. Manufacturers have also spent millions, and countless hours, perfecting emergency drills and procedures, that, when allied with the high redundancy and reliability of systems on board, give considerable confidence that a safe outcome will be the end result of an in-flight emergency.'
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