Elbert - the information I quote was taken today from the "Pro's" area of the PADI website, and is entitled "Current recommendations for flying after diving". If the exam answers are different then it is those that are out of date and wrong. It is up to us as instructors to ensure that the material we teach, and the exams we administer, are fully current. If there are deficiencies it is up to us to make appropriate changes in anticipation of new exams being printed.

But I recall the three time limits of 12 hours, 18 hours and 24+ hours as having been around for many years. I must admit to having been wrong myself in that I mis-remembered that flying was defined as starting at 3000ft. That was wrong, but so is 1000ft (see above). I don't recall any time at which 1000ft was the extant definition.

I haven't looked at the OW exam questions & answers, but I don't remember 1000ft from there.

Thinking again, diving at altitude is considered to start at 1000 feet. Could that be what you are thinking of?