DL MM DM in Chicago. While I am not exclusive to DL I am preferential to DL with AA coming in second and WN a distant third. UA only when someone is spurting arterial blood and I have to get there quickly.
My reasons...
1. On-time performance is superior to other carriers I am willing to use
2. Management of IROPS is far better than AA and WN that will both tell you to go pound sand (and I am EXP on AA)
3. Hard product is pretty good by North American standards
4. ATL in the winter and DTW / MSP in the summer
5. Lots of TATL options which is my most frequent int'l travel direction
6. LGA to NYC (yes, it's a sh@thole but it's convenient to my office in Manhattan)
7. SCs getting better, food options have improved and well liquors are better than the swill served at AA and UA clubs
8. Int'l hard product up front is FAR superior to UA (some 2-4-2 and 2-3-2 configurations with rear-facing seats) and AA with some 2-3-2 configurations.
9. Front line staff generally professional, polite and responsive.
10. Woodford.
