Elbert - I finally got around to looking up the "flying after diving" recommendations. I couldn't find them on DAN's website but I did on PADI's. The bold sections are my emphasis, not theirs.

General Comments
Recent experimental trials indicate the risk of decompression sickness (DCS) decreases as the preflight surface interval increases. Based on these studies, the Workshop reached the following consensus recommendations. These recommendations apply to flights at cabin altitudes between 600 metres/2000 feet and 2400 metres/8000 feet and to divers who are without DCS symptoms. Work by Buehlmann, which was used by the US Navy Diving manual, suggests that immediate ascent to 600 metres/2000 feet altitude is possible with low DCS risk. In 1999, the US Navy adopted more flexible procedures based, in part on Buehlmann and Vann et al. Following these recommendations reduces DCS risk but does not guarantee that a diver will avoid DCS.

For Dives within the No-Decompression Limits
Single Dives - A minimum preflight surface interval of 12 hours is suggested.
Repetitive Dives and/or Multiday Dives - A minimum preflight surface interval of 18 hours is suggested.

For Dives Requiring Decompression Stops
A minimum preflight surface interval greater than 18 hours is suggested.

Flying after diving recommendations need not be considered for flights to ambient/cabin pressures less than 600 metres/2000 feet.


So your statement above:-
Minimum of 18 hours before flight no mater whose rules your going by and the definition of altitude is above 1000 ft.
appears to be incorrect.