Transcript for 'Catastrophic Electrical Failure' on Passenger Jet
For the airlines, it's been a summer feeled with near misses, bird strikes and bad behavior by crews and passengers alike. We are learning tonight about a new air scare. A passenger jet made and emergency landing when a pie yot reported a, quote, catastrophic electrical failure. Abc's senior national correspondent jim avila details what happened next. Reporter: First clue of a problem for passengers on board alaska air 539 from ontario, california, to seattle. A chorus of angry infants. All the babies were crying at the same time. Reporter: Ears popping plane-wide as the 737 with 131 passengers and five crew momentarily loses enough cabin pressurization to cause a painful alert that something is wrong. My ears about blew up on me. Reporter: Up in the cockpit, pilots send an emergency call from 25,000 feet asking for priority landing at san jose airport. Telling controllers they are in the midst of a catastrophic electrical failure with loss of some flight controls and cabin pressure. 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 decent. Pilots thinking the electrical system is malfunctioning. But mechanics find it's a simple mechanical control near the landing gear telling the plane it's on the ground, not flying, turning off pressurization and the auto pilot. If it thinks it's on the ground, I wants to pull the throttles all the way back so that there is no more thrust coming out of the engine. Reporter: Alaska air says a backup system immediately restored air pressure in the cabin. The oxygen masks were never deployed. And the pilots took the flight controls. When the systems are not working properly, they need to know how to manually fly their airplane and bring it back safely. Reporter: It has been a summer of air scares. In june, there was a problem at o'hare, where an american airlines flight skipped off the runway, because of a problem with its landing gear. And then, in las vegas, a hydraulics problem sent a jetblue airplane into emergency landing mode. Over the last two years, this has been a very safe period for aviation. No fatal dents.
This transcript has been automatically generated and may not be 100% accurate.