How common are plane engine fires and bird collisions? An expert explains after American Airlines emergency

An American Airlines flight made an emergency landing at its departure airport in Columbus, Ohio, Sunday morning after a bird allegedly struck the engine.

“Mayday. Mayday. Mayday, American 1958. We’ve had a bird strike and an engine failure,” the crew said when reaching out to controllers, according to CNN.

The Boeing 737 commercial jet returned to John Glenn Columbus International Airport about 30 minutes after taking off at 7:45 a.m. en route to Phoenix, according to the tracking site FlightAware. No one was injured, and the Federal Aviation Administration is investigating the incident.

Video of the plane appears to show flames shooting out on one side as the aircraft made its way back to Columbus.

"Damn geese! First time seeing a fire and being involved in an emergency landing!" Ryan Brink, who was on the flight, posted on his Facebook page, along with a photo showing what appears to be blood smeared across part of the aircraft's exterior.

In a statement, American Airlines attributed the incident to a "mechanical issue.” John Glenn Columbus International Airport tweeted that the emergency landing involved a “reported engine fire” but later tweeted a correction saying that “the aircraft experienced mechanical issues, not an engine fire.”

Yahoo News spoke with Kristy Kiernan, associate director of the Boeing Center for Aviation and Aerospace Safety at Embry-Riddle Aeronautical University, to better understand what can cause fiery mechanical issues on commercial aircraft. This conversation has been lightly edited for length and clarity.

Officials aren't referring to this as an "engine fire," but photos and video of the incident show what appear to be flames coming out of the plane. What's the difference between an engine fire and a "mechanical issue" that appears to cause fire from the engine?

"Flames coming out of an engine may appear to be engine fire," Kiernan said. "However, it may not meet the indications of the fire occurring within the engine but outside the combustion chamber. Engines are always on fire — that's how they create thrust — but it's a controlled ignition process. So something that produces flames that appear to be coming out of the engine may not activate engine fire indications in the cockpit or in the engine. In either case, something unexpected and undesired is happening within the engine, and the outcome of that in terms of what the cockpit crew does is probably similar, but it may not be an 'engine fire.'"

On Thursday, a different American Airlines flight due to fly from North Carolina to Dallas was canceled due to an engine fire, according to the FAA. How common are engine fires and mechanical issues on commercial aircraft?

"One thing you can say for sure is that it's extremely rare," Kiernan said. "Mechanical malfunction, engine fire, engine shutdown, engine failure — all of these are extremely rare events. I think it's important to keep in mind that we have 45,000 flights handled by air traffic control every single day, so when these events happen, they're very salient, but they're also extremely rare."

What is usually the cause of an engine fire on an airplane?

"A couple of broad categories," Kiernan said. "Under the umbrella of mechanical malfunction, you can have a leak of a flammable fluid where it's not supposed to be, like hydraulic fluid or fuel can be leaking due to a problem in the plumbing, basically. Or you can have a failure of some of the metal components within the engine.

"Foreign object damage — in the form of, normally, birds — can also lead to engine fires. And when these things happen, they don't kind of just happen. There's usually some kind of manufacturing, maintenance or an operational process that can be improved. For example, the most famous bird strike event — which didn't result in engine fire but did result in failure — is the Hudson River Landing. And that resulted in some recommendations from the NTSB, including different ways of certifying engines."

Apparently a bird played a role in the emergency landing in Ohio on Sunday. How common is it for birds to collide with aircraft?

"The rate of bird strikes in the U.S. was 2.83 per 10,000 departures for the period from 2009 to 2018," Kiernan said. "Of these, only 2 to 8% result in any aircraft damage.

"Usually, almost always they're inconsequential. The airplane is designed to be able to withstand a bird impact. However, sometimes the circumstance is more than what the engine is designed to ingest, or it causes some particular damage. And there are certain parts of the profile of the takeoff, cruise and landing where the aircraft is more vulnerable to that because of the speed of the engines or the proximity to the ground. So it's not an uncommon thing, but what is uncommon is for it to actually damage the aircraft."

What usually happens when there's an engine fire or a mechanical issue that's causing a fire? What do the pilot and crew do next?

"There's something that's probably familiar to anybody who follows aviation, which is: aviate, navigate, communicate," Kiernan said.

"So in the broadest sense, what every pilot will do is, first of all, aviate. Make sure that the airplane is flying safely. And then, in the case of an engine fire, what you want to do is shut down the engine and secure the source of fuel to it. So you shut down the engine, you secure the fuel, activate any kind of fire extinguishing capability that you have. And those are the highest priorities.

"And then once you've got the engine shut down and the fire extinguished, the urgency decreases a fair bit because you can fly on one engine for a while — though obviously, you don't know what caused the fire and you want to get on the ground as soon as possible. So that's really the next step, is that once you've maintained aircraft control, you've shut down the engine and you've completed the checklist, then you make sure no smoke is entering the cabin, and then you just conduct a single-engine landing."

What should passengers do if there's an engine fire or mechanical issue onboard?

"What the flying public should do is read the safety card and pay attention to the safety brief before anything happens," Kiernan said. "That is the time to have your plan. Every single pilot flying commercial airplane has handled dozens of engine fires and failures throughout their career. So it's not new to them. They've done it dozens of times in the simulator. And passengers can do the same thing: be prepared, read that card, pay attention to the safety brief. It's like a minute long, and it could save your life.

"In addition to that, I would say, stay seated and follow the flight attendant instructions. And if something does happen, pay attention, because you might be a pretty good source of information for the NTSB. If you hear or see or smell anything, just pay attention and keep your wits about you.

"And if the flight attendant tells you to evacuate the airplane, just leave everything behind. Don't grab stuff!"