Even if Spirit and Frontier airlines win regulatory approval to merge, the low-fare competition at Minneapolis-St. Paul International Airport will remain shaped by Sun Country Airlines.

The locally based carrier had more than three times the market share at MSP that Spirit and Frontier had combined last year. And late Monday, Sun Country released financial results that showed it is nearly back to profitability without government assistance or accounting tricks.

"We closed out 2021 in a very strong way," Jude Bricker, the company's chief executive, said in a statement, noting that financial results beat its targets.

He and other executives noted the carrier, like others, in December endured staffing and flight difficulties from the fast spread of the omicron variant of the COVID-19 virus. The airline's overall capacity ended up being 6% less in the last three months of 2021 than it was in the July-September period.

Sun Country also was forced to cancel a huge swath of flights on two days during the last week of the year — aggravating passengers and sharply raising its costs — because of a computer system failure.

"Demand was modestly softer than expected in December, which we believe to have been due to the omicron variant," Dave Davis, the airline's chief financial officer, said. "Beginning in mid-January, we have seen a very strong rebound in bookings."

For the start of 2022, executives said they expect Sun Country's capacity to be 5% to 10% greater than it was in the first three months of 2019. Revenue could be as much as 14% higher.

Like many companies, Sun Country is not drawing comparisons to operations in 2020 and 2021, when COVID-19 disruptions render them meaningless.

For the last three months of 2020, Sun Country lost $600,000, or a penny a share. Revenue was $173 million, which was 5% higher than the last three months of 2019.

Minnesota travelers benefit from the pricing pressure that Sun Country, along with Southwest, Spirit and Frontier, place on Delta Air Lines, which dominates MSP with a 72% market share.

In announcing their proposed $6 billion merger, Frontier and Spirit said that their route networks are largely complementary. Combined, they would offer more than 1,000 daily flights to around 145 destinations in 19 countries.

Fort Lauderdale-based Spirit entered the Twin Cities market in 2015 and last year had a 2% share of passenger revenue at MSP. Denver-based Frontier started flying to MSP in 1995 and had a market share of under 1% last year.

A Frontier spokeswoman on Monday said she wasn't able to provide more details regarding the impact of the merger on the Twin Cities market.

Both airlines have service and reliability challenges, said Bob Mann, an aviation analyst in Port Washington, New York. "If it were my sandbox to play in, I would make sure we went from worst to first on a lot of these important metrics," Mann said.

Frontier and Spirit will continue to operate as separate airlines with a future name and headquarters location still in the works until the merger is complete, which is expected in the second half of the year.

The merged Frontier and Spirit carrier is likely to focus on keeping costs down so it can continue to offer low fares, Mann said.

"It's going to come down to how people execute," Mann said. "You rarely have an opportunity to do huge things in this industry and this might be one of those times."