It was only Estrada’s second trip on a plane and her first in 13 years. She was nervous and gave a quick thought to her husband and three kids at home. But she and her friends quickly got back to drinking hard lemonade, mapping out their weekend away from Iowa.

A few feet away, other passengers shared tips on attractions, buffets and the cheapest blackjack tables.

“You must see the pirate show,” one insisted.

Allegiant finds ways to profit on routes other airlines couldn’t make work, often swooping in after they pull out. This month, it started flying between Asheville, N.C., and Tampa, a route abandoned by AirTran after Southwest Airlines acquired it.

Like other discount carriers, Allegiant prefers small airports that charge airlines lower rents, even if they aren’t the most convenient. In Orlando, that means flying into Sanford, Fla., 30 minutes further from Walt Disney World than Orlando International Airport.

Frugal decisions like that helped Allegiant post a net profit of $78 million last year on revenue of $909 million. Its 8.6 percent profit margin was the highest of any U.S. airline, making it a darling of Wall Street.

The last five years have been good for airline investors. After a major spike in fuel prices in 2008 and a drop in business travelers, airlines tweaked their business models, adding baggage fees and cutting unprofitable flights. They started to make money and their stock prices climbed. While the S&P 500 climbed 26 percent in the past five years, an index of all U.S. airline stocks has tripled. Allegiant’s stock has done even better, increasing more than fivefold to $105.40

Allegiant has 64 planes and flies to 87 cities, but it’s tiny compared with an airline like United, which carried 20 times as many people last year, often on much longer flights.

The airline got its start in 1998 as a charter operation with one airplane. By February the following year, it had started scheduled flights between Fresno, Calif. and Las Vegas.

But its business struggled and less than two years later, it filed for bankruptcy protection. Maurice J. Gallagher, Jr., the airline’s major creditor and a founder of ValuJet Airlines, gained control during the reorganization and became CEO. ValuJet was a low-cost carrier that changed its name to AirTran after a 1996 fatal crash in Florida.

Gallagher moved the airline from Fresno to Las Vegas; secured a lucrative contract with Harrah’s to provide charter services to its casinos in Laughlin, Nev., and Reno, Nev.; and started to transform Allegiant into a low-cost carrier.

“The model evolved out of survival,” says Gallagher, who is still CEO.

By 2003, the airline started turning profits, and it hasn’t stopped. Gallagher’s nearly 20 percent stake in the airline is now worth more than $380 million.

Allegiant benefits from paying lower salaries and having work rules that are more favorable to management than at most airlines. Flight attendants with 15 years of experience are paid $34 for each hour their plane is in the air – $10 to $20 less than colleagues at larger carriers. Planes and crews typically end up at their home cities overnight, avoiding hotel rooms.

Wages could eventually shoot up. Pilots, flight attendants and dispatchers have all voted in the past two and a half years to join unions. The company has yet to sign a contract with any of them.