Operations were back to normal Saturday morning after a car crash caused a panic at Los Angeles International Airport.
Some people thought the crash sounded like gunfire.
The LAX Twitter account said about 60 flights were delayed, affecting 4,600 passengers.
The incident occurred three weeks to the day after a gunman sprayed bullets across a crowded Terminal 3, killing a Transportation Security Administration officer.
Los Angeles World Airports spokeswoman Nancy Castles said that shortly before 7:30 p.m., airport police responded to a report of shots fired at Terminal 5. When they arrived, they found that a traffic accident outside the terminal had caused a loud noise, prompting travelers to evacuate onto the sidewalk.
At the same time, an anonymous caller reported seeing a man with a weapon at one of the gates in Terminal 4, Castles said. Police responded, evacuating and sweeping the terminal “out of an abundance of caution,” she said. No gunman was found.
Castles said Terminal 4 was secured and cleared, and passengers were rescreened and continued their travels.
Witnesses described panic unfolding as law enforcement tried to grasp what was happening.
Peter Ward, a 34-year-old tech consultant from Australia, said he was at the Oneworld Lounge on the second floor of Terminal 4 when he saw some commotion downstairs.
“People were diving behind counters at the restaurants. Then people ran and evacuated very quickly,” said Ward, who watched the drama unfold below from the lounge windows. He turned to see several police officers running through the main entrance and into the terminal with guns drawn.
Many of them seemed to order passengers out of the terminal through the main entrance, he said.
At least two dozen more officers joined them, some with long rifles and others with bomb-sniffing dogs, Ward said. About 15 of them formed a “human barricade” near the security checkpoint, he said.
The rest of the officers continued to sweep the area downstairs, while Ward said he and other passengers in the lounge were told they were being kept on lockdown.