U.S. Air Force A-10 Thunderbolts (a.k.a. Warthogs) based in Michigan are flying over Sarnia, Ont., on a regular basis. The jets are designed to provide close air support for infantry troops. (Jacques Boissinot/Canadian Press)

First it was an American spy balloon floating over Sarnia, Ont., that irked the city's mayor — now it's American combat jets.

'I think the American government at least owes people on this side of the border an explanation of what they're doing and why they're doing it.'— Mayor Mike Bradley

Mike Bradley says residents of the city of 72,000 on the border with Port Huron, Mich., have been complaining for months about the fighter jets flying over the city's downtown.

"They shake the windows and they make a huge noise in the area that they're in," Bradley said. "In some cases it appears like a sonic boom when they pass over."

In the summer of 2009, Bradley complained to Prime Minister Stephen Harper about a U.S. government surveillance balloon flying over his city.

Frustration at being filmed by a foreign government, residents organized a protest called "moon the balloon," during which they bared their bottoms to the camera.

This year, Bradley has written to Foreign Affairs Minister Lawrence Cannon, asking him to investigate the fighter jets.

"I think the American government at least owes people on this side of the border an explanation of what they're doing and why they're doing it," Bradley said.

CBC News also contacted the Department of Foreign Affairs, but calls were not returned.

Jets allowed in Canadian airspace

The Michigan Air National Guard flies the planes out of its Selfridge base near Detroit.

Capt. Penny Caroll told CBC the jets — A-10 Thunderbolts more popularly known as Warthogs — frequently fly training missions near the border.

"And while we're over Canadian airspace we're required to climb to 1,000 feet, which can appear to be very low, but it's perfectly within the limits of our regulations," Caroll said.

While pilots have authority to enter Canadian airspace, Caroll said, the Michigan Air National Guard is aware of the concerns of its Canadian neighbours and is considering possible revisions to its training routes.