A real scare in the air. An alaska air jet, headed for seattle, carrying 131 passengers, forced to make an emergency landing on wednesday. Abc's jim avila is in washington with the latest on what went... See More
A real scare in the air. An alaska air jet, headed for seattle, carrying 131 passengers, forced to make an emergency landing on wednesday. Abc's jim avila is in washington with the latest on what went wrong. Good morning, jim. Reporter: Good morning, amy. It was another scare the faa is looking into. This one caused by a small part that malfunctioned, in telling the plane it wasn't flying at 25,000 feet, it was actually on the ground. The plane, then, shut down vital systems. A painful trip for the 131 passengers onboard alaska air 539, from ontario, california, to seattle. Finally landing overnight, five hours after takeoff, after a loss of cabin pressure forced the plane to make an emergency landing halfway through its trip. Emergency in progress. We have an emergency aircraft on 30 left in alaska. Reporter: The first clue in the passenger cabin, a chorus of screaming children. They said that the cabin had lost pressure. But that was kind of obvious with all of the babies crying from their ears hurting. Reporter: And ear-splitting pop. A painful alert. Up in the cockpit, pilots send an emergency call from 25,000 feet, asking for priority landing at san jose. The captain said, we're really sorry. But we have a problem with the cabin pressure. But it's under control now. And I felt like the plane was going down. And sure enough, it was. Reporter: An immediate but controlled descent. Pilots thinking the electrical system was malfunctioning. Mechanics later find it's a simple mechanical control near the landing gear, telling the plane it's on the ground, not flying. Turning off cabin pressurization, and the plane's autopilot. It's going to want to throw the throttles all the way back so there's no more thrust coming in the engine. Reporter: Alaska air says the cabin pressure was immediately restored. And the pilots took control. When all else fails and the systems aren't working properly, he needs to know how to manually fly that airplane and bring it back safely. Reporter: That's what they did, taking control, by hand, of that big jet. And flying it to safety like it was a little cessna.
This transcript has been automatically generated and may not be 100% accurate.