"Why does Delta Air Lines hate Palm Springs?" a reader recently asked. He also posed a less facetious question: How do airlines determine where to fly?

The question is key because sometimes changes in an airline's schedule can put a serious crimp on vacation plans. The man who called owns a second home in the California getaway. This season, Delta dropped all nonstop flights between the Twin Cities and Palm Springs; Northwest once covered the route with two daily nonstops.

Terry Trippler, the Minneapolis-based owner of www.theplanerules.com, says that personal feelings about a destination have nothing to do with major airline's flight plans.

"Sun Country used to fly to West Palm Beach because that's where Petters lived," Trippler said, referring to Tom Petters, the former owner of Sun Country Airlines. "But an airline like Delta would never do that." He points to smaller fleets and the need to fill seats as the main factors. Airlines must deploy their planes where the most people fly.

Since the merger with Northwest, Delta has many hubs and has cut overlapping or unprofitable routes, said George Hobica, president of www.airfarewatchdog.com. "Never a month goes by that an airline doesn't cut or add a route," he added.

Trippler suggests that the reader take Delta's nonstop flights between MSP and the Orange County airport, because he prefers using frequent-flier miles on Delta to buying tickets on Sun Country, which flies nonstop to the California destination from here.

"If [Delta] were making money, they would not drop the route, I promise," Trippler said.