I flew BA for the first times for work early on in my now retired career in the early 90's and they were usually a same day return and only happened from time to time and not every year.
My first leisure flight I went to SFO in Y around 1993 IIRC for my first leisure flight on a 747 IIRC and even today I still enjoy very much looking at the 747's and even more so when flying on one and my first ever Op up from ORD-LHR in 2000 on a 777 which was fab!
Other memories, including recently, my first 789 F trip so sometimes it's an aircraft memory too as well as my 1st time on BA as above.