▁made ▁the ▁following ▁recommend ations ▁for ▁flying ▁after ▁recre ational ▁div ing : ▁ ▁a ▁ 1 2 - hour ▁surface ▁interval ▁for ▁un cert ified ▁individuals ▁who ▁took ▁part ▁in ▁a ▁" res ort " ▁or ▁intro duct ory ▁sc uba ▁experience ; ▁ ▁an ▁ 1 8 - hour ▁surface ▁interval ▁for ▁cert ified ▁divers ▁who ▁make ▁an ▁un limited ▁number ▁of ▁no - de com pression ▁air ▁or ▁nit ro x ▁div es ▁over ▁multiple ▁days ; ▁and ▁ ▁substantial ly ▁longer ▁than ▁ 1 8 ▁hours ▁for ▁technical ▁divers ▁who ▁make ▁decom pression ▁div es ▁or ▁used ▁hel ium ▁breath ing ▁mix es , ▁as ▁no ▁specific ▁evidence ▁concerning ▁decom pression ▁or ▁hel ium ▁div ing ▁was ▁available . ▁These ▁recommend ations ▁apply ▁to ▁flying ▁at ▁an ▁alt itude ▁greater ▁than , ▁or ▁cabin ▁pressure ▁less ▁than , ▁an ▁alt itude ▁equivalent ▁of ▁ 2 , 0 0 0 ▁feet ▁( 6 1 0 ▁meters ). ▁ ▁NASA ▁astr onaut s ▁train ▁under water ▁to ▁simulate ▁the ▁weight less ness ▁and ▁occasionally ▁need ▁to ▁fly ▁afterwards ▁at ▁cabin ▁alt itudes ▁not ▁exceed ing ▁ 1 0 , 0 0 0 ▁feet ▁( 3 , 0 0 0 ▁meters ). ▁Training ▁div es ▁use ▁ 4 6 % ▁N it ro x ▁and ▁can ▁exceed ▁six ▁hours ▁at ▁a ▁maximum ▁depth ▁of ▁ 4 0   ff w ▁( 1 2   m fw ) ▁for ▁a ▁maximum ▁equivalent ▁air ▁depth ▁( E AD ) ▁of ▁ 2 4  