The passengers were stranded in four airport terminals and in 24 planes starting at about 1:30 p.m. Saturday because of a breakdown in the computer system. The system contains the names of arriving passengers and law enforcement data about them, including arrest warrants, said Los Angeles World Airports spokesman Paul Haney.
"That system allows our officers to make decisions on who we can allow to enter the United States," said Mike Fleming, a Customs and Border Protection spokesman. "You just don't know by looking at them."
Some of the computers were functioning again by 9:15 p.m., and authorities had begun slowly processing the huge backlog of passengers in order of their arrival.
The cause of the shutdown was not known, and there was no estimate on when the system would be repaired, Fleming said.
Authorities had begun using a backup system by 7:45 p.m. and were processing passengers in order of their arrival.
However, the system could only support half of the inspection booths normally used by customs officers, Fleming said.
Customs officials were working to divert incoming flights to airports in Ontario, California, and Las Vegas, Fleming said.
Terminals that normally accept international passengers have been full since at least 2:30 p.m., and passengers arriving since then have had to remain on the runway.
"This is just unbearable," said Gaynelle Jones, 57, who landed on a 13-hour flight from Hong Kong at about 2:15 p.m. and was still sitting on her plane five hours later. She said she had missed her connecting flight to Houston.
"We've already been on a plane for several hours, and they have no timeframe for when we'll be able to get off," Jones told The Associated Press from her cell phone.
Airport officials said the stranded planes were connected to ground power and passengers had access to food, water and bathrooms.
"People are getting a little stir-crazy, feeling claustrophobic," said Chris Cognac, 39, who was returning with a group of family and friends — including 10 children — from a week in Puerta Vallarta. The group had been sitting on the tarmac for five hours when he spoke by phone.
Passengers on his plane were in the aisles, holding their carry-on luggage, and ready to disembark when the flight crew asked them to return to their seats, Cognac said.
"Everybody's pretty angry with customs at the moment because they're not informing anyone of anything," Cognac said. "It's becoming a logistical issue with diapers."