Flying, or otherwise ascending, to a higher altitude having dived can predispose a diver to decompression illness unless there has been sufficient surface interval time to allow excess gas to diffuse from the body. If sufficient time has not been allowed and the ambient pressure is reduced, gas bubbles may form, or existing asymptomatic bubbles may increase in size and cause symptoms of decompression illness.

We can never be exactly sure when it becomes 'Safe to Fly' after a dive since it will depend on the bubble formation and how long it persists. Many authorities recommend that as a general rule, a diver should wait at least 24 hours before flying after making an air dive. Sometimes this may be overly conservative, while on other occasions it may not be conservative enough.

DAN Current Recommendations for Flying After Diving:

Dives within the No-Decompression Limits
• Single No-Decompression Dive
Minimum pre-flight surface interval of 12 hours is suggested
• Multiple Dives per Day or multiple Days of Diving
Minimum pre-flight surface interval of 18 hours is suggested

Dives Requiring No-Decompression Stops
There is little experimental or published evidence on which to base a recommendation for decompression dives. A pre-flight surface interval longer than 18 hours appears to be prudent.

Note 1
If a diver has had symptoms of decompression illness and has not received appropriate recompression treatment, flying can be risky even more than a week after the dive.

Note 2
After a long flight, one is often jet-lagged and dehydrated. Since a diver who dives in this condition may have an increased susceptibility to DCI, one is not advised to dive until after a complete recovery from the flight.