September 1981. JFK-KEF-LUX on Icelandair. Included a free bus from LUX to downtown Frankfurt. It was the cheapest way to get to Europe back then. I was on my way to spend some time roaming Europe prior to a semester abroad in Scotland.
I was in an A window seat and saw a spectacular northern lights show. I have booked A seats on nighttime TATL flights ever since, in the hopes of a repeat, but it has never happened. That and the couple next to me nitpicking about their kosher meal were the main memories of the flight.
I believe my first BA flight was a daytime JFK-LHR in 1988. Pre-lie flat aisle J seat in the first row of the upper deck of a 747. Back then the cockpit door was left open for takeoff and I got a great view.