Question: The Walter HWK 109-509 powered the first piloted aircraft of any type to exceed how many MPH in level flight?
Sentence (from "Armstrong Flight Research Center"): There, AFRC houses and operates several of NASA's Science Mission Directorate aircraft including SOFIA (Stratospheric Observatory For Infrared Astronomy), a DC-8 Flying Laboratory, a Gulfstream C-20A UAVSAR and ER-2 High Altitude Platform.
Relevant evidence: No