Southwest Airlines, the Dallas-based U.S. budget air carrier and the only U.S. air carrier to show profits regularly since the World Trade Center attacks of 2001, reported Thursday that it had first-quarter net earnings of $76 million, up from $26 million in the same period last year.

It is the first company in the U.S. airline sector to report first-quarter earnings. Southwest is expected to be the only airline to report profits. The nine largest U.S. air carriers are expected to report losses totaling at least $2 billion.

The Thursday report indicated that Southwest’s profits were aided by the airline’s purchase of fuel at prefixed prices. This move saved the airline $155 million in the quarter.

The report warned, however, that second-quarter fuel prices are likely to be somewhat higher than in the first quarter and that second-quarter passenger numbers will probably be down from last year’s numbers because of an early Easter break this year. Southwest also said it had increased available seats by adding seven new airplanes to its fleet.