I knew my first solo was coming up, because at 4pm on the Friday, I was strapped in ready to take off on my own, but the advancing cloud of rain was giving the instructor cause for concern. So we scrubbed, and I came back on the Monday knowing I'd be pretty much guaranteed to go solo..
Quite often someone will turn up at 9am on their 16th birthday, guaranteed to fly solo after having been as-good-as solo for the last few years