HOUSTON: Six people were killed when a pair of World-War-II-era planes collided in mid-air at a show in Dallas and crashed to the ground in a ball of fire, authorities said Sunday.

“According to our Dallas County Medical Examiner, there are a total of 6 fatalities from yesterday’s Wings over Dallas air show incident,” Dallas County Judge Clay Jenkins said Sunday on Twitter.

The tragedy, under investigation by federal agencies, involved a single-pilot Bell P-63 Kingcobra crashing into a larger Boeing B-17 Flying Fortress.

Only a handful of B-17s remain and mainly feature at shows or museums, acoridng to Boeing.