"A US Navy F/A-18C, a single-seat aircraft off of the USS Kitty Hawk, went down at approximately 3:45 p.m. EST today (2045 GMT Wednesday) during ongoing coalition air operations in support of Operation Iraqi Freedom," said the statement released at Centcom's forward operating base in Qatar.

"While the coalition does not discuss the details of ongoing recovery operations, it is committed to fully accounting for all coalition personnel. An investigation is ongoing.

"The name of the pilot is being withheld pending notification of next of kin," the statement added.

A Centcom spokesman said it was not clear how the plane came down although the US networks Fox News and ABC News said it had been shot down.

A US Army Blackhawk helicopter was shot down in Iraq on Wednesday, but there were conflicting reports between the Pentagon and US Central Command on the number aboard and the number dead.

A Defense Department official said that "preliminary reports say seven were killed" but Centcom would only say six people were aboard the troop transporter, adding that "casualties have not been confirmed at this point".

SPACE.WIRE