DALLAS -- Two historic military planes collided and crashed to the ground Saturday during a Dallas air show, federal officials said, sending plumes of black smoke billowing into the sky. It was unclear how many people were on board the aircraft or if anyone on the ground was hurt. Emergency crews raced to the crash scene at the Dallas Executive Airport. A Boeing B-17 Flying Fortress and a Bell P-63 Kingcobra collided and crashed around 1:20 p.m., the Federal Aviation Administration said in a statement. The collision occurred during the Commemorative Air Force Wings Over Dallas show. Several videos posted on Twitter showed two aircraft appearing to collide in the air before they both rapidly descended, causing a large fire and clouds of black smoke to billow into the sky. The FAA and the National Transportation Safety Board were launching investigations.