Six people were killed when a pair of World-War-II-era planes collided in mid-air at a show in Texas 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 incident at Dallas Executive Airport involved a Boeing B-17 Flying Fortress and a smaller Bell P-63 Kingcobra, the Federal Aviation Administration said Saturday. Dallas Mayor Eric Johnson called the incident “a terrible tragedy,” adding that videos of the incident “are heartbreaking.” Multiple videos posted on social media showed dramatic scenes of the smaller plane descending toward the lower-flying B-17 and crashing into it as both flew in loops around the airport. After the collision, the planes appeared to break apart into several large pieces before crashing to the ground and exploding in a ball of fire, creating a huge plume of black smoke. The crash scattered debris across the airport grounds as well as on a strip mall and a nearby highway, which was closed for hours, Johnson said. Fire and rescue vehicles were already at the show in case of an emergency and responded immediately, authorities said. An estimated 5,000 people were in attendance at the event Saturday, a few miles south of downtown Dallas. Air show events planned for Sunday were canceled. The FAA said its agents and the National Transportation Safety Board would investigate the incident. Hank Coates, the chief executive of the Commemorative Air Force (CAF), whose planes were involved in the accident, said the B-17 “normally has a crew of four or five,” while the P-63 is operated by a single pilot. He said the pilots who operate the planes during such shows are experienced volunteers with “very thorough training” and are often retired military pilots. The Allied Pilots Association, the collective bargaining agent for American Airlines, confirmed earlier that two of its retired members died in the accident. Both planes were based in Houston, the Dallas Morning News reported. The CAF has some 180 vintage aircraft that fly roughly 6,500 hours per year in air shows, tributes to veterans, and training flights, according to Coates. The B-17, a four-engined bomber, played a major role in winning the air war against Germany in World War II. With a workhorse reputation, it became one of the most produced bombers ever. The CAF said the B-17 involved in the crash, which bore a Texas Raiders logo on its nose, was one of only five of the bombers that could still fly out of the 12,731 initially built. The P-63 Kingcobra was a fighter aircraft developed during the same war by Bell Aircraft, but it was used in combat only by the Soviet Air Force. Safety has long been a concern at air shows. Seven people died on October 2, 2019 when a B-17 crashed during a vintage aircraft show in Connecticut.