Flying after diving

At a glance

How flying after diving works to prevent DCS

When a diver breathes compressed air underwater, nitrogen from the air dissolves into their blood and tissues. The amount of nitrogen absorbed depends on the depth, duration, and number of dives. This is a natural physiological process. During a slow, controlled ascent, and during surface intervals, this dissolved nitrogen is gradually released from the body through breathing, without forming harmful bubbles. This process is called off-gassing.

Flying in a commercial aircraft means ascending to an altitude where the cabin pressure is significantly lower than at sea level. Typically, commercial aircraft cabins are pressurised to an equivalent altitude of 1,800-2,400 metres (6,000-8,000 feet). This reduction in ambient pressure acts similarly to a rapid ascent from a dive. If a diver has insufficient time to off-gas residual nitrogen after their last dive, this sudden decrease in pressure can cause the dissolved nitrogen to come out of solution too quickly, forming gas bubbles within the body's tissues and bloodstream. These bubbles are the cause of decompression sickness.

The recommended surface interval before flying allows the body enough time at sea-level pressure to safely eliminate most of the excess nitrogen absorbed during diving. By adhering to these guidelines, divers significantly reduce their risk of experiencing DCS when exposed to the lower cabin pressure during a flight. Dive computers often provide a 'no-fly' time countdown, which should always be followed, and divers should always err on the side of caution with longer surface intervals if possible.

Diving after flying vs. Flying after diving

What flying after diving means for your liveaboard trip

For liveaboard trips, adherence to flying after diving guidelines is meticulously planned by operators. Typically, the final day of a liveaboard itinerary will be structured to allow for sufficient off-gassing time. This often means that the last day of diving will involve fewer dives, shallower dives, or even no dives at all, depending on the length of the required surface interval and the departure schedule.

Liveaboard operators and dive guides are well-versed in these safety protocols and will communicate the 'no-fly' period clearly to all guests. Guests should always consult their dive computer for a personal 'no-fly' countdown, as this device tracks individual dive profiles and provides a customised recommendation. It is important to remember that these are minimum guidelines, and conservative approaches often recommend extending these intervals further, especially after multiple days of repetitive diving.

Ignoring flying after diving recommendations can lead to serious health consequences, potentially spoiling the end of an otherwise fantastic dive trip. Divers should plan their travel arrangements, particularly their return flights, with a generous buffer zone after their last scheduled dive. Many liveaboards schedule their last dive early on the final full day, allowing for a substantial surface interval before disembarkation and travel to an airport.

DAN's Flying After Diving Guidelines (Recreational Dives)

Common misconceptions

Myth: As long as I don't feel symptoms, I'm fine to fly. Fact: Decompression sickness (DCS) symptoms can be delayed, appearing hours after the dive or even after flying. Feeling well immediately after diving does not guarantee safety, as sub-symptomatic bubble formation can still be dangerous when exposed to reduced atmospheric pressure.

Myth: My flight is short, so the risk is minimal. Fact: The duration of the flight does not mitigate the risk of DCS. The primary risk factor is the change in atmospheric pressure from sea level to cabin altitude, which happens during ascent, regardless of how long the flight lasts. Even short flights can precipitate DCS.

Myth: I only did shallow dives, so I don't need to wait as long. Fact: While shallower dives may accumulate less nitrogen, official guidelines still recommend a minimum surface interval of 12 hours for single no-decompression dives and 18 hours for multiple dives. It's safer to adhere to established protocols regardless of perceived depth, as individual physiological responses can vary.

Myth: My dive computer says I'm clear to fly, so I can fly immediately. Fact: Your dive computer's 'no-fly' countdown is a critical safety feature and should always be followed. However, it provides a minimum. Many divers and organisations advocate for a more conservative approach, especially after multiple days of diving, to add an extra buffer of safety. Always err on the side of caution.