I'm curious about when you need to start your engines if you want to take-off on time. For instance, my first flight yesterday, yipee, from EHAM to EHBK I started the engines of the Dornier 10 minutes before I was supposed to take-off, but I could take of nearly 10 minutes after the listed take-off time. Is there some sort of "rule" here, or do you have to find out for yourself?