What is the fastest airplane?

In the actual flying world, who knows for sure. The F-35, F-22 et al can haul a$$, but the top speeds are classified. The SR-71 is no longer in service, but at one time was the fastest. Being the fastest gains you nothing except PR. It will not win the pilot a victory in an ACM environment. Training and pilot aggressiveness do that.

SR-71, wasn't the x41 a rocket? If so, are you considering rocket powered as a plane or a rocket? which the X-41 did about mach 2.50 if my memory is correct, and the SR-71 I do believe has a record well over that speed of about 3500+ mph. EDIT: Mr AUDU is right also about the F-22, but since the top speed is classified, I didn't count it as the fastest, just because we don't know yet. EDIT: Ugii, the scramjet technology (although we know it's out there) has not officially been sanctified as actual technology, it's as far as we know still just a theory. Scramjet technology is still in Black Opps., so you are not going to know any speed that it does, just what certain individuals have leaked it out to do. Have you physically seen a scram jet? No, you have not. So as far as official speed records, it's still the SR-71.

Officially, the SR-71. However I firmly believe the USAF has a replacement that is faster. The USAF had the SR-71 for many years before they admitted it existed.