The North American XB-70 Valkyrie is rolled out at Palmdale, Calif. Designed to fly at three times the speed of sound and at altitudes above 70,000 feet, the XB-70 is originally planned as a manned bomber, but funding limitations allow for only two aircraft, to be used strictly for testing and research.
The KC-Z4, a blended wing body tanker concept being developed by startup JetZero, could fuel larger groups of aircraft at longer range to hold more targets at risk, company officials say.