It is very uncommon for both engines on modern aircraft to stop working, but three things can make it happen. This is why we thought to take a look and see how far a plane can fly when its engines fail. 

Bird strikes could cause engines to fail

The first and most common reason why a plane would lose both engines is a bird strike. An incident like this is most likely to happen when the aircraft is taking off or landing and is often due to large birds like geese and seagulls.

Once the birds are ingested into the engines, the fans seize up, and the engines instantly fail. Now with no forward thrust, what was once a fast jet is nothing more than a glider.

Planes are also equipped with a ram air turbine (RAT). When the aircraft senses engine failure, the turbine drops from the belly and generates power from the air passing under.

Where to land?

The captain will immediately ask the co-pilot for a damage assessment and look at their instruments to see if the fans are not turning. If this is the case, the captain would not waste time trying to restart the engines but look for the best place to land. More often than not, this will be the airport that you just took off from or the one you were landing at.

A Mayday call will go out over the radio, and a request to land immediately and have emergency services available will be made. Once this is done, the pilot will inform the cabin crew of a "no time available emergency." The captain will then ask the first officer to put the electrical power back on as soon as it is available and start the glide slope into the airport. 

The plane needs to land at a low speed

Once the runway for landing is selected, the captain quickly assesses its glide path into the airport using the runway's Instrument landing system (ILS). The pilot will also deploy the landing gear early to create drag.

Now, the goal is to put the aircraft down at the lowest possible speed to help with the braking and bring the plane to a complete stop.

Glide ratio

When it comes to gliding ratios, all aircraft are different, meaning they will lose altitude at a different rate. This calculation will determine how far a plane can fly without the engines' thrust.

For example, say the plane has a lift to drag ratio of 10:1 it means that for every ten miles of flight, it loses one mile of altitude. If the aircraft was at the height of 36,000 feet (seven miles), the plane could fly for 70 miles before hitting the ground. A scenario like this could happen if engine power was lost due to the two causes that we did not mention yet. These are flying through volcanic ash or running out of fuel.

Back to the bird strike incident, we talked about most engine failures happening at a much lower elevation when taking off and landing. In the case of US Airways Captain Chesley Sullenberger, his Airbus A320 hit a flock of Canada geese at an altitude of just under 3,000 feet. Too far away to return to La Guardia or Teterboro Airport in New Jersey, Sully had no option to put the plane down on the Hudson River. Miraculously, all 155 people aboard were rescued by nearby boats. 

This is proof to passengers that if both engines fail, there is an excellent chance that even if the plane cannot make it to an airport, it could still all end well!

Air Canada flight 143 

As we pointed out earlier in the glide ratio, the higher up you are when the engines fail, the further you can glide. Two incidents that come to mind were both due to running out of fuel. The first of the two happened in the summer of 1983 when due to a miss calculation, Air Canada flight 143 ran out of fuel at 41,000 feet (12,000 m).

The aircraft, a Boeing 767, was en route from Montreal to Edmonton when partway through the flight, they realized that they did not have enough fuel for the journey. The cause was that Canada was converting to the metric system, and the ground crew fueled the jet in pounds rather than kilograms giving them half the fuel they needed for the flight.

Now out of fuel and too far to reach the closest airport (Winnipeg), the captain decided to land the plane at a former Royal Canadian Air Force base in Gimli, Manitoba. The aircraft landed safely after having glided for 45 miles with no injuries to the passengers and crew.

Air Transat Flight 236

The second incident involved Air Transat Flight 236 from Toronto to Lisbon in Portugal in 2001. This time it was not down to a fuel miscalculation but faulty maintenance on the Airbus A330-200.

As the plane was just over halfway across the Atlantic Ocean warnings started to sound about a lack of fuel prompting Captain Piché to divert to Lajes Air Base in the Azores. Now approximately 65 nautical miles (120 km; 75 mi) from Lajes Air Base, the aircraft lost thrust at an altitude of 33,000 feet (10,000 m).

At a descent rate of around 2,000 feet (600 meters) per minute, Piché estimated that they might have to ditch in the ocean before manually spotting the airport. Now to lose altitude, he performed a series of maneuvers before safely landing in the Azores. In total, the aircraft gilded without power for almost 100 miles.

Have you ever been on a commercial airliner that had to make an emergency landing without power? If so, we would love to read about your experience in the comments.