U.S. carrier Southwest Airlines said on April 7 that its traffic rose slightly in March compared with the same period last year, while unit revenue soared 22 percent.

The Dallas, Texas-based company said its traffic rose 0.4 percent year over year. But its unit revenue, or revenue per available seat mile flown, jumped 22 percent, indicating that airline industry is recovering from its deep decline.

Southwest has reported continued increase in its unit revenue, a key measure of revenue. It's unit revenue jumped 14 to 15 percent in January, and the same figure climbed to 16-17 percent in February.

The company said its load factor, or percentage of seats filled, rose to 81 percent, setting a record for its March load factors. It's the ninth straight month for Southwest to set a monthly record for load factors.

Air-travel demand and revenues fall sharply in late 2008 and through the first half of 2009 as fliers began cutting back on travels due to the global recession.

But the airline industry has seen improved revenue and demand since the latter part of 2009 as capacity cuts reduced the supply of seats and fliers came back.

Continental Airlines said earlier this month that its unit revenue rose 4.5 to 5.5 percent in March and US Airways reported a 9 percent increase in its March unit revenue.