NASA Administrator Jared Isaacman teased plans for a new high-speed X-plane with an SR-71 Blackbird-like silhouette, and an SR-71 on display at NASA's Armstrong Flight Research Center has disappeared since May. The aircraft, tail number 844, was the last Blackbird produced and last flew in 1999; satellite imagery confirms it has not been seen in months, raising speculation about a potential return-to-flight program.