LAX police officers boarded the plane about 10 p.m. and investigated the incident. A photograph posted online of one passenger's phone shows it connected with the full-strength WiFi hotspot.
Officials, though, determined no crime had been committed, police Sgt. Karla Ortiz said.
"Passengers were interviewed and cleared to continue with their travel plans," she said in a statement.
Nevertheless, the incident prompted the airline to cancel the scheduled flight, stranding many passengers in Los Angeles for a day.
Passenger Anthony Simon, who appears to work in digital communications, wasn't pleased and took to Twitter to express his frustration.
"Thanks to the idiot who did this meaning I won't get back to London for another day. #aa136," he wrote, attaching a link to a KABC-TV story about the incident.
The flight was expected to take off Monday, Ortiz said.