At around Mach 3, the temperature rise from the intake compression, added to the engine compressor temperature rise, reduced the allowable fuel flow because the turbine temperature limit did not change. The rotating machinery produced less power, but still enough to run at 100% RPM, thus keeping the airflow through the intake constant. The rotating machinery had become a drag item and the engine thrust at high speeds came from the afterburner temperature rise. Maximum flight speed was limited by the temperature of the air entering the engine compressor, which was not certified for temperatures above .