You just get used to whatever units you're working in. If you'd been trained in radians when learning how to fly, everything would be fine. It would be funny

You just get used to whatever units you're working in. If you'd been trained in radians when learning how to fly, everything would be fine. It would be funny though to hear ATC clear someone to land on runway pi/2. That's probably not as succinct as runway 9, but people would be used to it if they learned it in their primary training. The real problem though is switching costs. There are tens of thousands of planes out there and more than a million pilots. To switch all of the compasses, GPSs, flight computers, heading indicators, etc. as well as retrain a metric pantload of pilots would be ludicrous for no appreciable gain. Canada suffered through a problem similar to this when it went metric, and ended up with the Gimli Glider. http://en.wikipedia.org/wiki/Gimli_Glider http://en.wikipedia.org/wiki/Gimli_Glider Don't get me wrong though. I love the metric system and think it's great, however first and foremost we are creatures of practicality. If US dominance in the world slips over the next few generations, I would imagine it will at some point join the rest of the world and abandon imperial measurements.