Diving, flying and altitude

In short

After a dive, your body still holds excess nitrogen, which it eliminates over several hours. Flying or going to altitude too soon lowers the pressure around you and can trigger decompression sickness, even after a perfectly conducted no-stop dive. Recognised guidelines set minimum intervals, from 12 to 24 hours or more depending on the dives. Plan your trip accordingly: the last day is a no-diving day.

Why it matters

Decompression sickness during a flight is particularly hard to deal with: help is far away and the aircraft cannot always divert. It can also happen on the way home, when crossing a mountain pass. These situations are avoidable: all it takes is respecting an interval and planning the end of the trip well.

Why flying and altitude increase the risk

During the dive, your tissues absorb nitrogen; during the ascent and the following hours, they eliminate it slowly. Tables and computers are designed for this elimination to happen safely at sea-level pressure.

At altitude, ambient pressure is lower: an airliner cabin is pressurised, but to a pressure equivalent to an altitude of around 2,000 to 2,400 m. This extra pressure drop amounts to an additional "ascent" that the dive calculations did not plan for. Nitrogen still present can then form bubbles. The same happens on the road, in the mountains, or in a cable car.

Recommended intervals

The most widely quoted guidelines come from a Divers Alert Network (DAN) workshop held in 2002, for a flight on a pressurised airliner by a diver without symptoms:

Dives made	Minimum interval before flying
A single no-decompression dive	12 hours
Several dives in a day, or several days of diving	18 hours
Dives with mandatory decompression stops	Substantially longer than 18 hours (24 hours or more is often advised)

These intervals are minimums. They do not guarantee that no accident will occur; a longer interval reduces the risk further. Training agencies, dive centres and doctors may recommend more cautious intervals, often 24 hours after a trip with repetitive dives. The same precautions apply to going to altitude by road (pass, mountain resort): ask for advice if your route climbs significantly.

Any abnormal sign during or after the flight (pain, tingling, intense fatigue, vision or speech problems) must be reported immediately to the crew or emergency services, mentioning that you have been diving.

The computer's no-fly time

Most computers display a no-fly indication after the dive, or a time to wait before flying, calculated from your dives. Respect it, and use the longer of the computer's value and the guidelines above. Do not switch computers or reset yours during this period.

Planning a diving trip

• Last day without diving: allow at least 24 hours between the last dive and the return flight, taking the actual take-off time into account.
• A lighter last dive: shallower and without mandatory stops the day before leaving.
• Trips to altitude: a mountain excursion during the trip follows the same rules; schedule it before the dives or at the end of the trip, after the interval.
• Hydration and rest, which are part of general decompression sickness prevention.
• Insurance: check that your insurance covers diving and repatriation.

What about diving at altitude?

Diving in a mountain lake is a different matter: decompression parameters must be adapted to the low atmospheric pressure. See the specialty dives guide.

Key takeaways

• Flying or going to altitude after a dive increases the risk of decompression sickness.
• At least 12 hours after a single no-stop dive, 18 hours after several dives.
• After mandatory stops, substantially longer than 18 hours; 24 hours or more is often advised.
• Respect your computer's no-fly time, and use the longer interval.
• The last day of the trip is a no-diving day.

Further reading

After a scuba dive, the watch's widgets and complications show residual nitrogen and the recommended delay before flying; after mandatory stops, the recommendation not to fly is kept. These indications replace neither medical advice nor your dive computer. The guides on decompression and dive computers complement this one.