MANAMA, Bahrain (AP)—At least two other mix-ups with civilian planes by U.S. warships occurred in the Persian Gulf, one of the world’s busiest air corridors, before the USS Vincennes shot down an Iranian airliner, American sources said Tuesday.

All 290 people on the Airbus 3000 were killed when the plane was hit Sunday. A six-man team of U.S. experts led by an admiral arrived Tuesday to begin a confidential investigation.

Dozens of aircraft fly over the gulf each day, may on long-distance flights between Europe and Asia with stops at Dubal, Bahrain or Kuwait. The Iran Air jet was on a regularly-scheduled short hop across the Strait of Hormuz from Bandar Abbas to Dubai.

U.S. officials have said the Vincennes fired two anti-aircraft missiles at the plane in the mistaken belief it was an Iranian F-14 fighter. Iran says the Navy shot the plane down intentionally.

A U.S. officer said privately he knew of an incident “about a month ago” in which an airliner thought an American warship was trying to order it to change course when the ship was talking by radio to a different plane.

“The problem was bleed-over from one frequency to another, which sometimes happens because of harmonics,” he said. “The ship was trying to determine the position and identity of an aircraft, a non-commercial plane, and this other aircraft heard it and thought the ship was talking to it.”

He would not reveal the ship involved, but said he was unaware of any incident involving the Vincennes. The officer said he did not know what airline owned the jet involved.

About 16 U.S. warships are in the gulf at a given time. People on the bridge of one last month counted the lights of about 20 high-flying aircraft in an hour.

Another U.S. military source described an incident in mid-June in which a U.S. missile frigate, making its first trip into the gulf through the Strait of Hormuz, briefly locked its weapons radar on an airliner, but quickly realized the mistake.

“The best explanation for something like that is inexperience,” said the informant, who also insisted his name not be used.

“These crews are always nervous when they come into the gulf for the first time,” he said. “They know it’s a war zone, but they don’t know exactly what to expect. And one thing they don’t seem to get the word on is how much commercial air traffic there is out here.”

The Washington Post said Tuesday the Vincennes, which arrived in the gulf May 27, figured in an incident last month in which it “attempted to redirect” a jetliner in a way that caused United Arab Emirates officials to fear a collision of two commercial planes.

Quoting an air-traffic control official in the Emirates it did not identify, the paper stated the incident June 8 resulted in an official protest to the U.S. Embassy in Abu Dhabi. It stated the embassy declined comment.