Ok, technically I am cheating here, but I looked this up on the Regional Airline Associate page http://www.raa.org/carriers/topairports.html
and the data is a bit old 1998. Here goes...
1-DFW (American Eagle and ASA)
3-LAX (American eagle, Horizon, Skywest (Delta Connection and UAExpress)
4-IAD (Atlantic Coast Airlines)
5-ORD (Eagle, Air Wisconsin, UFS, Great Lakes, et al)
6-PIT (USAirways Express)
7-SEA (Horizon and Skywest (UAExpress)
8-BOS (too many to mention)
10-MIA (Eagle et al)
and if my data is wrong then TELL ME!!! But I don't see any surprises here. Do you???
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia