Two historic military aircraft crashed into each other on Saturday at an air show in the United States’ city of Dallas, the Associated Press reported.

The collision took place at the Dallas Executive Airport, about 16 km from the city’s downtown area. Videos on social media showed the two planes falling to the ground and bursting into flames.

A World War II Boeing B-17 Flying Fortress and a Bell P-63 Kingcobra were involved in the collision at the Wings Over Dallas air show.

Mayor Eric Johnson said that the number of casualties was not confirmed till Saturday afternoon, according to CNN.

Hank Coates, the president of the Commemorative Air Force, said that the B-17 aircraft normally has a crew of four to five persons. “That was what was on the aircraft,” he said. The P-63 aircraft has a single pilot, Coates said.

“I cannot release the number of people in the manifest or the names on the manifest until I’m released to do so by the NTSB [National Transportation Safety Board],” he said.

However, a labour union representing American Airlines pilots – the Allied Pilots Association – said on Twitter that two of its former members were among those who died in the crash. The association identified them as Terry Barker and Len Root.

The Dallas mayor said that no spectators or others on the ground were reported to be injured.

Meanwhile, Coates said that the aircraft involved in the collision were safe and well-maintained, according to CNN. “The pilots are very well-trained,” he said. “So it’s difficult for me to talk about it, because I know all these people, these are family, and they’re good friends.”

Coates said that most persons flying aircraft at such air shows are volunteers who undergo a strict training process. Several of them are airline pilots, retired airline pilots, or retired military pilots, he added.