My first flight in any airplane was in a 707 from SF to Portland around 1968. I remember being thrilled by the rapid acceleration on takeoff - something I hadn't really expected but I found pleasurable. I also liked the food - it was pretty good, as I recall. Can't remember the airline, but it was probably American or United.
My most favorite flight was in an old DC-3 from Tikal to Guatemala City around 1978. The engines were turboprop but the interior looked unchanged from the 30's - leatherette seats with stainless tube frames that could have been off a 30's PCC streetcar. We flew low and slow and although I had an aisle seat the view was amazing.
My favorite modern airline is Virgin Atlantic. I flew a lot on business related travel in the 90's, and the flight from SF to London stood out as the best experience. By contrast, I found most shorter hop flights on United to be dreadful. Surly flight attendants, little concern for travelers' actual needs. I remember once a flight attendent taking $20 from me for a set of headphones, then taking an hour or two to return the change, and then only grudgingly.I can only assume it's gotten worse since 9/11. Haven't flown much since then, and can't say I miss the airborne Greyhound bus experience or the hotel rooms, which however nice all start to look, smell, and feel the same.
I was very glad, however, when they banned smoking from US flights. There was no smoke-free zone on flights that restricted smoking to the rear of the plane. The air recirculation systems made sure of that.
I recall during my hippier days flying World Airways from Oakland to Honolulu in the 70's. I was really jonesing for a joint - which I had in my carry-on - but I remember a military looking guy sitting in a jump seat just in front of me, glaring at me, so I refrained from retreating to the restroom to light one up.
The strangest flight I had was on Aloha Airlines island hopping in Hawaii in the early 80's. I remember the outer wall of the cabin would flex when climbing so much that it nearly crushed my fingers that were gripping the handrest near the window. A year or two later an Aloha Airlines jet lost the top of its cabin in flight from metal fatigue. I always wondered if it was the same jet.
My naughty passenger moments included transporting camp fuel in an aluminum bottle in the luggage compartment - I didn't realize it was taboo. Fortunately it was a strong bottle with a good seal and it didn't leak a bit. On the flight back though I had to dump the contents out before checking the backpack. Another time I listened to AM radio on my waterproof Walkman... marveling at how the stations came and went so quickly over the mid-west. Then the flight attendent came by and made me shut it off - a few minutes later the pilot apologized that we'd be slightly delayed because we were slightly off course... never did that again...