The famed Thunderbirds are grounded after a pilot lost his life during a training exercise. Nellis Air Force Base is investigating the death of Major Stephen Del Bagno, a Thunderbirds pilot who was killed in Thursday's F-16 crash. "We are mourning the loss of Major Del Bagno," said Brig. Gen. Jeannie Leavitt, 57th Wing commander. "He was an integral part of our team and our hearts are heavy with his loss. We ask everyone to provide his family and friends the space to heal during this difficult time." Before joining the team, Del Bagno was an F-35A Joint Strike Fighter evaluator pilot and chief of standardization and evaluation with the 58th Fighter Squadron at Eglin Air Force Base, Florida.