Southwest Airlines Monthly Traffic Report Apr-2012

The largest U.S. domestic carrier had steadily booked rising traffic for much of last year with help from its acquisition of low-cost rival AirTran.

The airline said its April load factor, or the percentage of seats filled, slipped to 79.8% from 79.9% a year ago, while capacity declined 1.9%.

Southwest estimated its passenger revenue per available seat mile--a closely watched measure of performance for the industry--rose 7% to 8% from last year.