CHARLOTTE, N.C. -- A popular low-cost airline in our area continues to add flights amid growing safety concerns.

NBC Charlotte has been looking into Allegiant Airlines for months now, and this week, a new investigation shows Allegiant breaks down more mid-air than any other major U.S. airline.

The airline flies out of Concord and is getting set to add more flights later this month.

South Charlotte mom Jennifer Branham says she flew Allegiant once with her daughter out of Concord-- but won't ever fly the low-cost airline again.

"I'm flying with my child-- I want to be on the safest airline as possible."

For months there have been questions surrounding the safety of Allegiant Airlines with reports of mid-air issues from flights across the country; this summer the FAA even did a special evaluation of the airlines and said, "The evaluation found a number of deficiencies".

And now the Tampa Bay Times has published the results of an investigation they did analyzing federal aviation records. The Florida paper found Allegiant planes are four times more likely to break down mid-air than any other major U.S. airline.

"Is allegiant less safe than other airlines, based on what the times found, perhaps yes," says Seth Kaplan.

Kaplan runs an airline watchdog website and says Allegiant has old planes and doesn't seem to do a good job of maintaining them.

"This is an airline that’s been growing very rapidly and clearly has some issues maintaining it’s fleet."

The Times found in 2015, Allegiant jets were forced to make unexpected landings 77 times for serious mechanical issues-- and almost half the fleet broke down mid-flight at least once in that same year-- in some cases because of failing engines.

"It's a concern. I trust they're working on it-- having this out in public not only a safety issue, also bad business."

The FAA says they've been working closely with Allegiant to address all the issues they found during that earlier evaluation.

NBC Charlotte tried to get a comment from the airline but have not heard back.