"Origins of words" by Susie Dent, Countdown 24/10/17 (leading edge, pushing the envelope, flat spin)

I've been talking recently about words that began their life at sea. So, many, many words in English have nautical origins behind them. So, I thought I would look at aviation today. So, words and expressions that were born in the skies. We're going to is start with "leading edge". We talking about something that is leading edge, it's at the vanguard of development, it's right there at the forefront. It was, to be fair, first found on the seas as well, but when it came into aviation terminology, it meant the foremost edge of an aerofoil, especially a wing or again a propeller blade. There's another one which again you might think of as management speak and that's "pushing the envelope". Slightly annoying, pushing the envelope, but it means to extend the boundaries of what's possible, thinking outside the box, if you like. That goes back to 1940s, where in aviation parlance, an envelope or flight envelope, the definition is a set of limiting combinations of speed and altitude or speed and range possible for a particular aircraft of aircraft engine. And so, to push that envelope is to test it beyond its limits, almost, which of course is an important thing when you researching an aeronautical capabilities. Finally, we talk about being in a "flat spin", often, these days, if we're really agitated or slightly panicked about something. Probably, you can guess this one. It does go back to a serious situation for the pilot which may well lead to a sense of panic, and that's the aircraft descending whilist staying almost horizontal. Not a very nice experience at all. That goes back to 1917. So, all of those began in the skies.