Army special operations helicopters on a training exercise buzzed around the small city of Port Angeles, Wash., late Thursday in an episode that the mayor says "terrorized my city."
An Army official apologized Friday for the unannounced training mission.
Dozens of alarmed residents called police to ask what was going on.
"No one had any warning about the helicopters, no one said anything afterward, and today city officials had to spend hours just trying to find out what had happened — who had invaded Port Angeles," said Cherie Kidd, mayor of the Olympic Peninsula city about 60 miles west of Seattle.
The Army said the helicopters involved included both twin-engine Chinooks and Blackhawk attack helicopters.
The training exercise involved part of the 160th Special Operations Aviation Regiment, which is based at Fort Campbell, Ky., but has individual units in various locations, said Sgt. Jimmy Norris, an I Corps spokesman at Joint Base Lewis-McChord near Tacoma, Wash. Part of the 160th is based at Lewis-McChord, he said.
"Our watch commander last night reported that we received 'dozens of calls' complaining about low-flying helicopters over the city," Deputy Police Chief Brian Smith said.