DALLAS — Southwest Airlines Co. is making money even with higher fuel prices, thanks to full planes and rising fares.

CEO Gary C. Kelly says based on passenger-booking trends, the airline expects strong revenue in the first quarter too.

Southwest said Thursday that it earned $152 million in the fourth quarter, up from $131 million a year earlier.

The increase came from gains on fuel-hedging contracts. Without those one-time gains, Southwest would have earned $66 million, or 9 cents per share, compared with adjusted income of $115 million, or 15 cents per share, a year ago.

Still, the results beat analysts' prediction of 8 cents per share, according to FactSet.

With the addition of AirTran Airways, which Southwest bought last year, revenue jumped to $4.11 billion, a tick below analysts' forecast of $4.12 billion.

Southwest carries more passengers in the U.S. than any airline, and it's the first to report fourth-quarter results, so its profit is likely to be seen as a precursor to figures from other carriers that report next week.

Fuel costs have weighed on the airlines, but they were able to offset that by raising fares repeatedly in 2011.

The average passenger on Southwest paid a fare of $140.18 in the fourth quarter, a 7 percent increase from a year ago.

Southwest paid more at the pump to fill its fleet of Boeing 737s, however. Fuel averaged $3.29 per gallon, up from $2.46 a year earlier, and Southwest's final fuel tab came to $1.49 billion.