GENERALLY....employee (or file) numbers beginning with 1xxxxx are L-UA, 2xxxxx are L-CO, and 3xxxxx are post-merger hires.

That said, I know several L-CO folks who have 1xxxxx numbers. I haven't seen any L-UA with 2xxxxx numbers.

Just passing on info. I've flown with great people and wack jobs from both sides in equal proportions.