Seat choice matters most
Aisle, near a galley, ideally row 1 of an economy section if possible. The illusion of being able to stand and walk reduces the trigger dramatically — most people who use this strategy never actually need to use the aisle, just to know they could.
Cabin air is constantly refreshed
Modern aircraft cabin air is fully replaced every 2-3 minutes via HEPA filters. It is genuinely cleaner than a typical office or restaurant. The 'stale air' feeling is psychological, not real.
What to do if it builds mid-flight
Stand up. Walk slowly to the bathroom or galley and back. Drink cold water. Splash cold water on your wrists. Most cabin-crew teams are trained in supporting passengers through claustrophobia — they will quietly help if you ask.