Several deaths are feared after two World War II planes collided at an air show in Dallas, Texas. The number of victims has not yet been confirmed, said Mayor Eric Johnson on Saturday evening. But spectators on the ground were not harmed, he wrote on Twitter.

Up to six crew members were on board the two planes that collided in mid-air and then crashed, the organizer said. It was a Boeing B-17 Flying Fortress bomber and a Bell P-63 Kingcobra fighter. There were up to five people in the first machine, and only the pilot in the second.

Videos in the media and social networks show how the fast fighter crashes sideways into the four-engine Boeing, which breaks apart and both machines then fall to the ground. Then an explosion and a fireball can be seen.

He could not say anything about possible victims because the federal authorities are now investigating, the organizer said. Officially, there was initially no information on possible deaths. However, a pilots' union said two of its former members died aboard one of the planes.

It is still unclear exactly how many people were in the two machines, the US aviation authority FAA said at the request of the German Press Agency. In addition to the FAA, the US Transportation Safety Board (NTSB) is also investigating the accident.

The accident happened at a World War II commemoration show that drew around 4,000 visitors. On Friday, the United States celebrated Veterans Day, a holiday honoring veterans.

The organizer told journalists that he could not explain the accident. Neither machine would have performed any risky manoeuvres. The planes are also carefully maintained. The pilots used are very experienced and come from commercial aviation or the military. "There is a very rigorous process of review and training," he added.

The event, which was due to continue on Sunday, was canceled after the accident.

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