Because they happen to like the aircraft that that reg number goes with. For instance, in the chat room & on Yahoo/MSN instant messengers, I use N607P, the old Piedmont City of Charlotte Pacemaker (767-200ER). Why? I flew my fist widebody flight on this plane, and I used to live in Charlotte. I'm sure other users have similar reasons.
My nick also doubles as the rego for Finnair's first MD-11. It is also the first passenger MD-11 to enter service and to make the first revenue flight as well. A lot of history with this beautiful plane
My License plate (As of September 2003) will be N717JG... N representing the beginning of the registration number of an aircraft. 717 representing my favorite aircraft. and JG representing my Initials.
BTW -- This is not a ripoff, but more of an idea from this aircraft registration.
BR715-A1-30... I had a similar idea for my license plates. I wanted 'N777UA' for the first United 777 but I figured that 99% of the people looking at it wouldn't know or care what it stood for, so I just went with 'Hvy Jet'
The story behind my user name is that my dad was working for Capitol International Airways. Eventually our family would take a trip with Capitol in 1976 and the first leg out from JFK to Rome was on N907CL. The trip back was on N911CL. My brother ended up working for Capitol, and I did in 1984 right before they went under.