Passengers flying from Ontario, Calif., to Seattle today said a chorus of angry infants was their first clue of a problem aboard Alaska Airlines flight 539.
"All the babies were crying at the same time," said passenger Roslyn Richardson, who was flying with her husband and 20-month-old son.
Fliers said their ears also started popping as the 737, carrying 131 passengers and five crew members momentarily lost cabin pressurization.
"My ears about blew up on me," said Dick Peck. "We're halfway from Ontario to here and we're up to our max altitude and ... my ears started hurting. ... And I looked around and everyone else was grabbing their ears."
In the cockpit, pilots sent an emergency call from 25,000 feet to Federal Aviation Administration controllers, asking for priority landing at San Jose Airport. They told controllers that they were 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," his wife, Carol Peck, said.
Thinking the electrical system was malfunctioning, pilots opted for an immediate yet controlled descent.
Mechanics later found that an "air-ground censor," a simple mechanical control near the landing gear, had malfunctioned.
The censor had relayed to the airborne plane that it was on the ground and the aircraft had turned off the automatic flight controls and cabin pressurization.
"If it thinks it's on the ground, it's gonna wanna pull those throttles all the way back so that there is no more thrust coming out of the engine," said ABC News consultant Stephen Ganyard, a former fighter pilot and deputy secretary of state.
The pilots took over the plane manually and a backup system corrected the pressurization. There was no deployment of masks and Alaska Air said a backup system had immediately restored air pressure in the cabin.
"When the systems are not working properly, they need to know how to manually fly their airplane and bring it back safely," Ganyard said.
A spokesperson for the airline told ABC News that Alaska Airlines was making sure its passengers reached their destinations today.
Alaska Airlines swapped out a smaller plane that had been scheduled for a noon flight from San Jose to Seattle for a larger aircraft to accommodate larger number of fliers. Passengers like Richardson, however, were taking a shuttle to Oakland, Calif., and then flying to Seattle -- arriving eight hours later than originally expected.
"I'm just glad we're safe," she said. "That's what we were thinking at the end."