UAL Corp., the parent of United Air Lines, has hired Goldman Sachs & Co. to advise it on the possibilities of merging with another carrier, according to Crain's Chicago Business. There's been a fair amount of chatter of late about some sort of deal, with the likeliest candidates being Continental and Delta. If it happens, there would be huge ramifications for L.A. travelers. At LAX, United is the second-largest carriers, based on numbers of passengers.