The F-15C Eagle fighter jets are single-seaters

Both men were able to eject and were picked up during a rescue operation off the Florida panhandle, but one of the unnamed pilots later died.

The surviving pilot is said to be in good condition.

The planes are believed to have collided while practising basic manoeuvres on Wednesday afternoon.

The weather was clear.

'Great loss'

The Eglin air force base in Florida had suffered "a great loss", said Col Tom Harmer, commander of the 33rd Fighter Wing, 58th Fighter Squad, in a statement.

"My heart goes out to the family and friends of our fallen airman."

Both pilots had substantial experience, Col Harmer said.

The US temporarily grounded F-15C jets after one failed while training in Missouri last November.

Most were back in service by January, but others have been grounded indefinitely after defects were found.