It can be either. The Lightning was IAS limited at low level due to the probe, yet at high level it was one of the best supersonic machines. The Tornado F2/3, when clean, was initially unlimited-other than by total thrust over total drag as you describe. I have certainly seen 840 KIAS at 250 feet over the sea, apparently the speedo stopped reading at 999! The F3 was subsequently limited to a lower KIAS for "other" reasons. During this sort of thing the fuel gauge was a blur.
Last edited by Spon Clayton; 30th Apr 2008 at 08:20.