Delta Airlines passengers see more trouble at major U.S. airport

There are a number of carriers, often called the "big four," that currently control three quarters of the U.S. market: Delta Air Lines , American Airlines , United Airlines and Southwest . For example, Allegiant Air has found success focusing on leisure passengers with a network of small cities and travelers looking for experiences such as weekend getaways. At Seattle-Tacoma International Airport, Alaska Airlines has managed to succeed even as major carriers such as Delta have tried to squeeze into its home turf.