One word: Xanax. Diazepam made me slightly woozy/headache-y and you generally feel slightly drugged up. Xanax takes away all the anxiety without a single side effect. You are still perfectly able to think clearly and remember everything about the flight. However all the memories are pleasant, even if the plane is bumping like fuck over turbulence. It's the strangest thing to explain, but because you remember things positively, it actually helps to improve your fear with each subsequent flight. If you're too anxious to sleep on long-haul flights then you can up the dosage to a level which knocks you out. It takes a bit of trial of error and obviously with caution since you don't want to overdo it while up in the sky.
I find it's the absolutely perfect solution to fear of flying because it's a situation that's extremely self-limited. An average person flies about 1-2 times a year, or even less. Taking benzos twice a year is never going to lead to addiction and the relief it provides is indescribable. If you got kidney stones once a year you would certainly not refuse to take stronger painkillers for that one event. So I don't get the point of spending so much time & money for courses, therapy, breathing exercises etc when there's a magic bullet that will erase all your fears instantly and only for the duration of the flight.
The biggest caveat is finding a doctor to prescribe it, unfortunately because of the potential of abuse. I was lucky to find a GP who trusted me sufficiently and one prescription has lasted me 5 years. I've only taken it while on board a plane and I genuinely look forward to travel now instead of dreading it in the weeks leading up.
My fear is also not the plane crashing, but a complex mix of being out of control, unable to escape, emetophobia (people around you being sick, being sick yourself), sensory overload from being in tight space with too many people and too much noise etc. Many fear of flying courses might work well for NT people who just need proof that planes don't crash but that wouldn't touch the edges for me. I also have ADD with racing thoughts so I know my problem is fundamentally neurological and medication was the only thing that really solved it.