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Mach 15 is about 5104.35 meters per second.

The only plane that was slated to move that fast was the (unmanned) NASA X-43, which recorded speeds over Mach 10. The X-43A used a rocket booster to get to speed after being dropped out of a B-52. A scramjet engine powered the aircraft. The X-43D was envisioned to be able to reach Mach 15. However, it never proceeded beyond the feasibility study phase.

Astronauts reach well over Mach 15 during re-entry: they can reach speeds as high as Mach 25.