Two vintage military aircraft collided and crashed to the ground during a Dallas air show on Saturday, according to federal officials, sending columns of black smoke into the sky. Both the number of passengers and the existence of any casualties on the ground were unknown.

Emergency services flocked to the crash site at Dallas Executive Airport, some 10 miles (16 km) outside of the city centre.

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Onlookers were seen setting up orange cones around the bomber’s disintegrating remains, which were in a grassy location, in real-time televised footage of the incident.

According to a release from the Federal Aviation Administration, a Bell P-63 Kingcobra and a Boeing B-17 Flying Fortress collided and crashed at around 1:20 pm. There was a collision during the Commemorative Air Force show Wings Over Dallas.

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“At this time, it is unknown how many people were on both aircraft,” the FAA statement added.

The massive four-engine bomber known as the B-17 was a cornerstone of American air superiority during World War II. Soviet forces mostly used the Kingcobra, an American fighter plane, during the conflict. The vast majority of B-17s, according to Boeing, were destroyed after the end of World War II, and today there are just a few that are primarily displayed at museums and aviation shows.

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Videos posted on Twitter appeared to show the bomber and fighter plane meeting, sending both plummeting to the earth with a loud explosion and generating a huge ball of fire and smoke.

A webpage promoting the event refers to Wings Over Dallas as “America’s Premier World War II Airshow.” Veterans Day weekend, Nov. 11–13, was set aside for the display, which promised to feature more than 40 World War II-era aircraft.

Investigations were being conducted by the National Transportation Safety Board and the FAA.