My dad has kept a journal of all the flights I have been on, since the day I was born, including the flight registration number. According to the log, my first flight ever was on 7-APR-1972, on BOAC Flight 790, registration number G-ARVE from LHR to KUL. I was a month old then.
Thanks to the internet, here is a picture of the actual aircraft I flew on! You can view the aircraft's life story at http://www.vc10.net/Airframes/cn_807__garve.html.
As for me, I was not given a seat number but I did have my own baby bassinet. Probably the most legroom I have had ever when flying. Also got to hold the stewardess's hand!