I've been browsing the on-line ESP SDK. The section on .air files seem totally inadequate. It offers an overview of the compiler with some sample source files, but doesn't desribe all the tokens that are appear to be available.Is that as good as it gets, or do licencees get more detail?

That's as good as it gets. It's the FSX SDK with added ASM to create airfiles. I have an MSDN subscription and let's say I was a wee bit disappointed when it was first available for download.-Dai