Panel-popping plane deemed scary, but it's not dangerous

Scary but not unsafe: That's the assessment of aviation safety experts about an American Airlines flight during which the wall panels cracked loose, prompting an emergency landing at San Francisco International Airport.

The problem on the flight from San Francisco to Dallas began shortly after takeoff Monday, when passengers, still strapped into their seats, heard loud popping and ripping sounds. One said it sounded like bowling balls were falling from the overhead bins.

Several plastic interior panels snapped out and became pinned to the window seats in one row, exposing insulation. Passengers called for flight attendants and watched nervously as they inspected the damage.

It turned out to be a cosmetic problem -- not a crack in the airplane's skin that would have been far more serious -- but the pilot decided to turn the plane around anyway after checking it himself about 45 minutes into the flight.

There were no injuries. Here are things to know about the trouble:

Q: What the heck happened?

A: American Airlines says a duct between the panel and the metal skin of the aircraft failed and air forced the panels loose. The Federal Aviation Administration isn't disputing that.

Q: Still, it sounds pretty bad. Why not turn around immediately?

A: The cabin pressure was normal and oxygen masks didn't drop, meaning the problem was cosmetic, not a hole in the exterior. While planes can fly with a puncture in their skin, it is dangerous. The aircraft was safe to fly, according to American and several aviation experts.

Still, the decision to turn around also made sense. "In a day where we manage risk, why bother" flying on? said Carol Giles, a safety consultant. "They did the right thing."

Q: How often do these panels pop off?

A: Not very. Several experts said they had seen it happen on other aircraft, either as pilots or passengers. Boeing, the manufacturer of the 757-200 aircraft, declined to comment on whether the problem happened before.

Q: Was the plane just old?

A: The Federal Aviation Administration granted the plane's certificate to fly 19 years ago, according to government records. That makes it average age for American's fleet, airline spokesman Matt Miller said. He wouldn't comment on when it last went in for a heavy maintenance check that would have involved testing the ducts. All American planes are "in airworthy condition when dispatched for a flight," he said.

Q: Why would a duct like this fail?

A: American will try to answer that at its maintenance facility in Oklahoma, where the plane was flown Tuesday. There are various possibilities, among them a bad connection between two ducts, or a hole that wasn't caught during an inspection.

Or, "this kind of non-safety related part could just fail," said John McGraw, an aerospace consultant and former deputy director in the FAA's aviation safety service.

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Associated Press Airlines Writer David Koenig in Dallas contributed.

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Contact Justin Pritchard at https://twitter.com/lalanewsman