Hydrazine Test

Maintainers perform a hydrazine safety check on the agency’s quiet supersonic X-59 aircraft at U.S. Air Force Plant 42 in Palmdale, California, on Aug. 18, 2025. Hydrazine is a highly toxic chemical, but it serves as a critical backup to restart the engine in flight, if necessary, and is one of several safety features being validated ahead of the aircraft’s first flight.

Maintainers perform a hydrazine safety check on the agency’s quiet supersonic X-59 aircraft at U.S. Air Force Plant 42 in Palmdale, California, on Aug. 18, 2025. Hydrazine is a highly toxic chemical, but it serves as a critical backup to restart the engine in flight, if necessary, and is one of several safety features being validated ahead of the aircraft’s first flight.