Originally Posted by
tmiw
Letters in the name, perhaps? (e.g. 7A7) Though that might not be something Boeing will need to worry about for a while.
Originally Posted by
readywhenyouare
That's an interesting thought. The 787 was initially called the 7E7.
I think it actually goes back farther than that ... iirc the 767 concept was designated 7E7 and the 757 was 7N7 (for reference, I joined Boeing Commercial in 1978, transferred to Flight Test about six months later; was Test Director on the #4 767-200 and several other early production jets Dec 1981 to Sep 1982)