Two historic military planes have collided before crashing to the ground during an air show in Dallas, Texas.

It is unclear how many people were on board the Second World War-era bomber and fighter involved or if anyone on the ground was hurt after the incident at Dallas Executive Airport, about 16 kilometres from the city centre.

Live TV news footage from the scene showed people setting up a cordon around the crumpled wreckage of the bomber, which lay in a grassy area.

The Boeing B-17 Flying Fortress and a Bell P-63 Kingcobra collided and crashed around 1.20pm local time on Saturday, the US Federal Aviation Administration said.

Leah Block, a spokesperson for Commemorative Air Force, which produced the Veterans Day weekend show and owned the crashed aircraft, told ABC News she believed there were five crew members on the B-17 Flying Fortress bomber and one aboard the P-63 Kingcobra fighter plane.

The Houston-based aircraft were not giving rides to paying customers at the time, she said.

The collision occurred during the Commemorative Air Force Wings Over Dallas show.

The B-17, an immense four-engine bomber, was a cornerstone of US air power during the Second World War.

The Kingcobra, a US fighter plane, was used mostly by Soviet forces during the war. Most B-17s were scrapped at the end of the Second World War and only a handful remain today, largely featured at museums and air shows, according to Boeing.

Several videos posted on Twitter showed the fighter plane appearing to fly into the bomber, causing them to quickly crash to the ground and setting off a large ball of fire and smoke.

“It was really horrific to see,” Aubrey Anne Young, 37, who saw the crash. Her children were inside the hangar with their father when it occurred.

“I’m still trying to make sense of it.”

Air show safety – particularly with older military aircraft – has been a concern for years. In 2011, 11 people were killed in Reno, Nevada, when a P-51 Mustang crashed into spectators.

In 2019, a bomber crashed in Hartford, Connecticut, killing seven people.

The NTSB said then that it had investigated 21 accidents since 1982 involving Second World War-era bombers, resulting in 23 deaths.