How fast does the SR71 Really go?
The USAF has never really admitted to a true top speed, but most experts agree that the top speed of the SR71 is Mach 3.5. This is because of two simple reasons. First the glass in the windshield and second the engine spike The windshield limit the SR71’s top speed because its glass would begin to melt at speeds higher than Mach 3.5. The glass technology was, in 1964 when the Blackbird was made, at the highest they had the capability to make. Glass technology has not changed that much in since then when it come to handling the temperature variations that the SR does at high altitude and speed. The other main reason it cannot go faster is because even though the engine spike moves to slow down the super-sonic air (so the engines don’t unstart) to sub-sonic speeds, it can only do so up to a certain point. This point is around Mach 3.5 and depends on altitude and other atmospheric conditions. In effective and safe speed tests the USAF will not usually fly faster than Mach 3 and if the wea
