All sorts of crazy shit goes through my mind on a plane - engine is going to fall off, wing will break, pilot is suicidal, bomb in a suitcase.
What has helped me a little bit, in addition to 3-4 beers before takeoff, is looking at a site like flightaware.com, and seeing how many planes are in the air at all times, especially in the northeast US. And then I multiply that by some multiple to consider planes all over the world. And then I compare it to how many car accidents I see on the way to the airport.