Question: The Walter HWK 109-509 powered the first piloted aircraft of any type to exceed how many MPH in level flight?

Context paragraphs:
Armstrong Flight Research Center: The NASA Neil A. Armstrong Flight Research Center (AFRC) is an aeronautical research center operated by NASA.  Its primary campus is located inside Edwards Air Force Base and is considered NASA’s premier site for aeronautical research.  AFRC operates some of the most advanced aircraft in the world and is known for many aviation firsts, including critical support for the first manned airplane to exceed the speed of sound in level flight with the Bell X-1, highest speed ever recorded by a manned, powered aircraft (North American X-15), the first pure digital fly-by-wire aircraft (F-8 DFBW), and many others.  AFRC also operates a second site in Palmdale, Ca.  known as Building 703, once the former Rockwell International/North American Aircraft production facility, at Air Force Plant 42.  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.  David McBride is currently the center's director.

Douglas F4D Skyray: The Douglas F4D Skyray (later redesignated F-6 Skyray) was an American carrier-based fighter/interceptor built by the Douglas Aircraft Company.  Although it was in service for a relatively short time and never entered combat, it was the first carrier-launched aircraft to hold the world's absolute speed record, at 752.943 mph, and was the first United States Navy and United States Marine Corps fighter that could exceed Mach 1 in level flight.  It was the last fighter produced by the Douglas Aircraft Company before it merged with McDonnell Aircraft and became McDonnell Douglas.  The F5D Skylancer was an advanced development of the F4D Skyray that did not go into service.

Fastest propeller-driven aircraft: A number of aircraft have been claimed to be the fastest propeller-driven aircraft.  This article presents the current record holders for several sub-classes of propeller-driven aircraft that hold recognized, documented speed records in level flight.  Fédération Aéronautique Internationale (FAI) records are the basis for this article.  Other contenders and their claims are discussed, but only those made under controlled conditions and measured by outside observers.  Pilots during World War II sometimes claimed to have reached supersonic speeds in propeller-driven fighters during emergency dives, but these speeds are not included as accepted records.  Neither are speeds recorded in a dive during high-speed tests with the Supermarine Spitfire, including Squadron Leader J.R. Tobin's 606mph (Mach 0.89) in a 45° dive in a Mark XI Spitfire (date unknown) and Squadron Leader Anthony F. Martindale's breaking 620mph (Mach 0.92) in the same aircraft in April 1944.  Flight Lieutenant Edward Powles' 690 mph (Mach 0.96) in Spitfire PR.XIX PS852 during an emergency dive while carrying out spying flights over China on 5 February, 1952 is also discounted.  This would otherwise be the highest speed ever recorded for a piston-engined aircraft.

Ballarat Aviation Museum: Ballarat Aviation Museum is an Australian aviation museum located at Ballarat Airport in Ballarat, Victoria.  Among other exhibits it contains a CAC Wirraway, a Ikara anti-submarine missile, a Mignet Pou-du-Ciel, a PZL TS-11 Iskra and a Walter HWK 109-509 rocket engine, the type that was used to power the Messerschmitt Me 163 Komet.

History of unmanned aerial vehicles: An Unmanned aerial vehicle (UAV) is a type of aircraft which has no onboard crew or passengers.  UAVs include both autonomous drones and remotely piloted vehicles (RPVs).  A UAV is capable of controlled, sustained level flight and is powered by a jet, reciprocating, or electric engine.  In the 21st century, technology reached a point of sophistication that the UAV is now being given a greatly expanded role in many areas of aviation.

Walter HWK 109-500: The Walter HWK 109-500 was a liquid fuelled rocket motor developed by Walter in Germany during the Second World War.

Walter HWK 509: The Walter HWK 109-509 was a German liquid-fuel bipropellant rocket engine that powered the Messerschmitt Me 163 Komet and Bachem Ba 349 aircraft.  It was produced by Hellmuth Walter Kommanditgesellschaft (HWK) commencing in 1943.

Messerschmitt Me 163 Komet: The Messerschmitt Me 163 Komet was a German rocket-powered fighter aircraft.  Designed by Alexander Lippisch, it is the only rocket-powered fighter aircraft ever to have been operational and the first piloted aircraft of any type to exceed 1000 km/h (621 mph) in level flight.  Its design was revolutionary and its performance unprecedented.  German test pilot Heini Dittmar in early July 1944 reached 1130 km/h , an unofficial flight airspeed record unmatched by turbojet-powered aircraft for almost a decade.  Over 300 aircraft were built, but the Komet proved ineffective in its dedicated role as an interceptor aircraft and was responsible for the destruction of only about nine to eighteen Allied aircraft against ten losses.  Aside from combat losses many pilots were killed during testing and training.

Tupolev I-8: The Tupolev I-8 (also known as the ANT-13) was an experimental interceptor built in the Soviet Union in the early 1930s.  It was the first Soviet aircraft to exceed 300 km/h (162 knots, 186 mph) in level flight.  The aircraft was an exercise in developing the Polikarpov I-5 design by a group of engineers led by V. M. Rodionov, each of whom volunteered 70 hours of personal time to the project.

Bell X-1: The Bell X-1 was a rocket engine-powered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for Aeronautics-U.S. Army Air Forces-U.S. Air Force supersonic research project built by Bell Aircraft.  Conceived during 1944 and designed and built in 1945, it achieved a speed of nearly 1000 mph in 1948.  A derivative of this same design, the Bell X-1A, having greater fuel capacity and hence longer rocket burning time, exceeded 1600 mph in 1954.  The X-1, piloted by Chuck Yeager, was the first manned airplane to exceed the speed of sound in level flight and was the first of the X-planes, a series of American experimental rocket planes (and non-rocket planes) designated for testing of new technologies and often kept secret.

Supporting paragraphs: Walter HWK 509 Messerschmitt Me 163 Komet
Answer: 621