I used to until about February this year. As you say, it wasn't to do with fear of flying, but rather about not having the option to leave the aircraft immediately (which sounds daft, but it's irrational fear, so there's no point trying to explain that part...) Mine generally took on the form of hyperventilation and bronchospasm, so I'd get a suffocating sensation.

Sleeping pills and/or alcohol were not an option (I'm an ex-addict).

This also applied to other situations - particularly transport - London Underground, buses, trains... Even cars on a motorway. At times, even being in a labyrinthine office complex for a meeting or a church tower stairwell could have the same effect.

The three things that helped me were CBT, SNRIs and forcing myself to do the very things that made me panic. You can equip yourself to do this by:

• going for a medical checkup. If you know your oxygen absorption and lungs are healthy, then you've more rational ammunition to fight the panic.
• carrying a bottle of water with you. Sipping from a bottle of water can help interrupt hyperventilation.
• carrying something mindlessly distracting with you. Perhaps an (easy) puzzle or similar - remember you can't use electrical items at some of the most 'difficult' parts of the flight.
• carrying a paper bag. If you're hyperventilating, it can get your CO2 levels back to normal.
• recognising hyperventilation and being able to count (4s in, 4s hold, 4s out) the time you take to have your breaths.

Obviously, these are for a specific type of panic attack, but they did help.