Dallas ? Southwest Airlines Co. grew at its slowest rate in two decades in 2008, reporting Tuesday that its traffic and capacity grew only slightly last year.

Even so, the Dallas-based carrier is expected to be one of only a few U.S. carriers to report any growth during the year.

Southwest said its traffic increased only 1.6 percent last year.

Among the nation’s largest carriers, American Airlines Inc. on Monday said its 2008 traffic fell 4.8 percent. Continental Airlines Inc. said its traffic last year declined 1.8 percent. United Airlines Inc. saw 6.5 percent decrease in traffic as its capacity fell 4.5 percent.

For American, its capacity fell to its lowest levels since 2001.

Only AirTran Airways Inc. and Alaska Airlines Inc., two of the smaller major carriers, joined Southwest in reporting 2008 increases in traffic.