The incident occurred at 11:20 local time (19:20 GMT) on Monday while the aircraft was on a routine test mission. The crash sent a huge plume of black smoke into the air that could be seen for miles. BBC reported.
"Today, Edwards Air Force Base experienced a terrible tragedy, and we lost eight great Americans," Col James Hayes said, describing them as a "mixed crew of military, government civilians and government contractors".
The base earlier said that initial indications are that the crash "was not survivable".
The crew's next of kin are being notified and they will be named 24 hours after that, Hayes said in an afternoon briefing.
The crash was "totally contained" within the Edwards Air Force Base on the runway, Hayes said, and the base has temporarily grounded operations.
