The USAF is already flying bits of the AGM-183A ARRW.

Air Force conducts successful hypersonic weapon flight test

This was a “sensor only” captive carry, which presumably means something along the lines of a wholly non-functional mass/aerodynamics simulator. It doesn’t really look like the sort of thing that could get to Mach 20 with a meaningful payload.

The U.S. Air Force successfully conducted the first flight test of its AGM-183A Air Launched Rapid Response Weapon, or ARRW, on a B-52 Stratofortress aircraft on June 12 at Edwards Air Force Base, Californiahttps://t.co/N8wluNSayE pic.twitter.com/bdNrDRDpTr

— Edwards AFB (@EdwardsAFB) June 17, 2019