I saw an Aggressor III piloted by Garland Hamilton get clocked at 265 mph in a level pass. He had come out of a dive but had been flying level for 300-400 yards by the time he flew through the traps. I've read of a Ultra Viper D/F that got clocked at 269 MPH.

I'm sure there are turbine powered planes that travel in excess of 300 mph.

There are guy's out there with composite Bandits with Jetcat 160's in them, that's EASILY a 350 MPH plane.