I really don't know. My first Trans-Atlantic flight was when I was 10 days old, but the parents can't remember if it was BA or KLM.

I do clearly remember being on my first 777 with BA on the plane's maiden passenger voyage. More vaguely, I remember being on my first 747-400 and knowing enough about planes to tell the difference from the previous (200?) version. Something I'd struggle to do now apart from some vague knowledge about the number of windows on the UD and something about wing tips.