The SR71 Blackbird is the fastest plane on Earth. Mach 3 is simply the plane travelling at 3 times the speed of sound. Ejecting at mach 3+ is lethal though, the forces would tear you apart (literally).
That’s how a test pilot died. They were testing a prototype blackbird in the 1960s and the nose got ripped off (just behind the co pilot) mid-flight at very high altitude (can’t remember the exact figure) and at about mach 3. The co pilot was thrown straight out of the plane when the nose tore off but the main pilot was still in the cabin so he had to eject, but when he did, the force broke his neck instantly.
Fun fact (more like funny fact): In another failed flight the pilot ejected safely, landed in the sea, then accidentally opened his suit’s visor and drowned (a blackbird flight suit is much like an astronaut suit due the the altitude the plane reaches).
WRY have an alien burst out of your chest or have your spine and skull ripped out be a predator in one go?
(I’ve waited a long time to use this meme lol).