Two planes collide in mid-air _ Dallas air show crash

"Please, say a prayer for the souls who took to the sky to entertain and educate our families today."

The number of casualties are not yet confirmed, he said, but added that nobody on the ground had been reported injured.

The event's website states that several planes had been scheduled to do a flyover demonstration on Saturday.

The B-17 bomber played a major role in winning the air war against Germany in WW2.

The second plane, a P-63 Kingcobra, was a fighter aircraft used in the same war, but used in combat only by the Soviet Air Force.

The B-17 usually has a crew of about four to five people, while the P-63 has a single pilot, said Hank Coates, from the Commemorative Air Force which organised the event.

"This was a WW2 flight demonstration type air show where we highlight the aircraft and their capabilities," he told reporters.