Sid Kramer, a police officer at Dulles International Airport, was driving by the main terminal yesterday morning when his cruiser was rocked by what he at first feared was a tremendous explosion.

Passengers near the entrance scrambled for cover and crouched against the walls, Kramer said. Others said a hush descended over the building as police officers dashed about with their hands on their holsters.

The blast turned out to be a bolt of lightning that authorities say may have hit the terminal. While there was no damage, it rattled passengers, attendants and sales clerks, many of whom said they were worried about Muammar Qaddafi's threats of reprisals for American air strikes.

In particular, the blast frightened many passengers and workers who had no view from the huge windows in the main terminal of the rainstorm outside.

Cindy A. Chilcoat, a counter representative for Budget Rent a Car, said the lightning bolt "sounded like it was right in the airport. It sounded like a bomb. It startled everybody."

"The first thing I thought of was a bomb," said Traci Pollard, a cashier. "It really shook people up."

"I'm sure people thought: 'Muammar is here,' " said Kramer, "but it was just Mother Nature."