The Firefly's a good-looking aircraft, but the USAF grounded its fleet of 114 T-3 variants in '97 and withdrew them from service for good in '99 after a spate of incidents following the type's introduction in '94.
The T-3's problems were mainly due to the fact that the USAF had decided to re-engine the aircraft with the more powerful Lycoming AEIO-540 (in place of the usual O-235 or O-320), and -- more importantly -- to install an automatic mixture control servo 'off-the-shelf,' without additional testing.
As a result, a number of fuel metering events were experienced at altitude (not something to build confidence in newbie pilots!!). Other rumors at the time suggested the grounding was a political (i.e. NIH) issue.
There are still 50 or so aircraft rotting away at Hondo Airport in Texas. Not a pretty site.
I/C