The Cold War may be over, but the Pentagon says goodwill can go too far.

After learning that a Soviet pilot had been at the controls of a U.S. Navy Blue Angels F/A-18 fighter plane during an impromptu test ride at a July 8 air show at Kalamazoo, Mich., the Defense Department sent word to all the services: Don't let it happen again.

"I think it's kind of sad," said David Collier, a Kalamazoo air show liaison to the Soviet delegation. He said relations between the Soviets and Americans at an Ohio air show two weeks ago were markedly cooler because of the Pentagon ruling.

Lt. Dave Wray, a Navy spokesman, said the Defense Department ruled that Soviet pilots would not be allowed to fly in any U.S. aircraft, and that no American pilots would fly Soviet planes. Wray said no reason was given for the prohibition.

The Defense Department declined to comment, referring questions to the Navy.

"I don't think anyone had any concern that a ride in the back seat of an F/A-18 affords even a trained observer a technology leak," Wray said, noting that the Blue Angels plane is used only for show flying and for Navy training purposes.