I had been paxing fairly regularly from the age of 5 and never had a problem until I was 30. Booked a BM flight from LHR to AMS to spend a long weekend with an oppo and totally lost it on the flight. I knew it was irrational but every sound, change in engine note, turbulence, hydraulic noise had me a gibbering wreck. Got to Schiphol and had a panic attack at the thought of the flight back. I got the train and ferry.
I knew I had a few flights coming up so reported to the MO who sent me to a psychologist. She reckoned after much discussion that it was not having any control over any events that may happen that caused this episode along with a lack of knowledge of flight itself. I had a few chats with the ships flight commander and he suggested having a few hours instruction at a local flying school to get an understanding of how things 'work'. Did that and never looked back. Fell in love with flying again and as funds improved carried on with the training. May not work for everyone but it sorted me out. As mentioned above it could well have been a mental health episode triggered by stress at work/home, who knows?