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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.

‘‘We've been told several times at the (negotiating) table: If you don’t like this job, there’s the door,’’ says Debra Petersen-Barber, who has been an Allegiant flight attendant for eight years and is the lead negotiator for the Transport Workers Union of America. ‘‘We have no value. We’re easily replaced.’’

Thanks to its choice of aircraft, Allegiant has more flexibility than other airlines in deciding when and where to fly.

Instead of buying the newest, most expensive planes, the airline buys used, inexpensive jets. Its planes are 23 years old, on average, compared with the industry average of 14 years.

Each used MD-80 costs $3 million, compared with $40 million for a new Boeing 737 or Airbus A320 of similar size.

‘‘When you have such little investment in an aircraft, you only fly it when it’s going to be full of passengers,’’ says Peter B. Barlow, an aircraft finance lawyer at Smith, Gambrell & Russell. ‘‘Other airlines don’t have that luxury. They need to keep their aircraft in the air in order to make the economics work.’’

So on Tuesdays, when most of Allegiant’s customers are stuck in the office, the airline keeps nearly all its planes on the ground.

Flying older planes has drawbacks, though. They burn more fuel, something Allegiant combats by squeezing 166 passengers onto planes — 26 more than American Airlines has on comparable jets. They also have more mechanical problems, resulting in more delays.

One of every four Allegiant flights last year was at least 15 minutes late, the worst record in the industry, according to flight tracker FlightAware.

The bigger problem is if a mechanical issue forces a plane to be grounded. Given its limited schedule and packed planes, there usually isn’t another flight to book passengers on. Instead, they are left waiting six hours while a new plane is flown in.

Sometimes flights are postponed to the next day. In one extreme situation in March, more than 1,700 passengers flying to and from Hawaii saw multi-day delays, including one flight that was 52 hours late.

That’s a lot of time to kill at an airport bar.

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Scott Mayerowitz can be reached at http://twitter.com/GlobeTrotScott.