Thanks guys, I'm learning a ton.

Here's my table for UA then: If tail is NabcUA then the 'a' digit (first digit) indicates:

a digit aircraft type
------ ------------
1 744
2 777
3 733
4 320
5 752
6 767
7 777
8 319
9 735

But this leaves me perplexed... doesn't UA have more than 100 752s? And what number range to CRJs and EMs get? And what will they do with the rumored new 787s?