Originally Posted by
PTahCha
This is my take, but in general:
Hub cities - this one is obvious - ORD, DEN, GUM, IAH, LAX, EWR, SFO, NRT, IAD
Focus cities, business centers, current/former international gateways - AUS, BOS, CLE, FLL, HNL, LGA, SAT, DCA, SEA
Legacy PMUA West Coast focus - SAN, LAS, PHX, PDX
Competitive OAL hubs - ATL, DFW, MSP, PHL
Contractual - SNA, MCO
International - HKG, LHR, MEX
This doesn't explain why, as an example, there are no United Clubs at SLC or MIA (where there used to be a RCC due to). # of flights and size of operations are probably determining factors.