Found it:
NORTH EAST USA & CANADA 1 - Baltimore, Boston,
Chicago Ohare, Detroit, Montreal Trudeau, New York, JFK,
Newark, Philadelphia, Toronto and Washington Dulles
SOUTH EAST USA & CARIBBEAN ISLANDS 1 - Atlanta,
Kingston Manley, Memphis, Miami International, Orlando
International and Tampa
SOUTH WEST USA & MEXICO 1 - Dallas Ft. Worth,
Houston, Los Angeles, Phoenix and San Diego
NORTH WEST USA & CANADA 1 - Denver, Minneapolis St
Pl, San Francisco, Seattle and Vancouver
Flights betw the cities in the zone, for 2500 Miles.
But when you look at, for some similar short(er) segments, the 15K miles are required.