US secret aircrafts – do they exist?

Do aircrafts like Aurora, lockheeds “Brilliant buzzard” and General Dynamics model 100 really exist?

The term Aurora was 1st seen in 1986 in a US DoD budget request for $80million. In 1987 the term Aurora disapeared, to be replaced by such terms as “Special Update Program” and “Selected Activities”. These programs recieved $100s of million funding.

It is claimed by some that these A/Cs exist but no convincing photos have been seen in the public domain.

Does Russia or even china have similar secret projects? What about the Eurpeans? especially the French and the British.