The US Air Force has unveiled its newest nuclear stealth bomber, the B-21, which will gradually replace aircraft first flown in the Cold War.
The first new bomber in 30 years could cost nearly $700m (£569m) each and can carry nuclear and conventional weapons.
Mr Austin said the plane would offer significant advances over existing bombers in the US fleet, stating that "even the most sophisticated air defence systems will struggle to detect the B-21 in the sky".
While the potential for an uncrewed flight was not mentioned during the ceremony, a US Air Force spokeswoman said the aircraft was "provisioned for the possibility, but there has been no decision to fly without a crew".
The first flight by a B-21 is expected to take place next year.
The US Air Force is planning to acquire at least 100 of the aircraft.
US unveils new nuclear stealth bomber