Your GPS Doesn't Work at Mach 2 Because It's Afraid You're a Soviet Spy

Fun fact: GPS technology has built-in limits based on speed and altitude. Basically, if a vehicle is moving faster than 1200mph or cruising higher than 60,000 feet, GPS shuts off. Why those numbers exactly? You can thank the commies.

The CoCOM, or Coordinating Committee for Multilateral Export Controls, was established in the early years of the Cold War to put an arms embargo on Eastern Bloc countries. After GPS was developed by the Defense Department, COCOM limits were put in place so that the government could be sure the technology wouldn't end up in commie-guided missiles.


Of course, the Cold War is over. That your GPS stops functioning when you're moving that fast or that high (which is to say not often) is because it's a relic of a bygone age. [Wikipedia via MAKE]


1200 MPH is about Mach 1.58 over the ground. In the American inventory, only the F-5, -15, -16, -18, -22, and -35, the T-38, and the B-1 have a chance at getting that, and most of those would need a stiff, jet stream tail wind to do so.

In my 900+ hours in the Tomcat, I only saw 1200 MPH over the ground once, 900 knots true air speed plus 200 knots of wind at my back. We were at about 40,000 feet over the Pacific, and, other than the increased wind noise over the canopy, it didn't seem very different than any other flight. I remember feeling a little weird knowing that if anything went wrong with the jet, we were way, way outside the ejection envelope.

I wish I had known about the alleged GPS limitation; I would have tried out my handheld.