The chair of Sun Country Airlines' board is threatening to ground its planes in the midst of the company's pay dispute with its pilots union.

A letter from Marty Davis to the union said the company's management has "begun the process of downsizing the airline, for what will need to be its ultimate shut-down."

The company declined to comment. The pilots union dismissed the letter as a bargaining tactic.

"We are disappointed Mr. Davis has chosen to respond to us with the threat of a shutdown," Capt. Brian Roseen, the pilots union's chairman, said in a news release Thursday.

"Sun Country pilots intend to show up for work tomorrow and continue to do our jobs the way we always have — safely, professionally and courteously," the statement said. "The Association looks forward to opportunities later this month to continue our good-faith efforts to reach a comprehensive agreement that reflects established pay and benefit patterns, and trusts that Company executives will participate with the same intention."

It's not unusual to hear dire warnings from management in a dispute like this, said aviation consultant Kit Darby.

"It is possible to take an airline to a point that it either can't — or management doesn't want to — continue," Darby said. "However, without the specific financial information, it's very difficult for an outside person or firm to evaluate the real status."

Federal records indicate the carrier has been consistently profitable since 2009. The pilots union argues that no other sizable airline pays pilots less for flying Boeing 737s.

The union, which would not disclose pay rates, says pilots haven't had a pay raise in 5 years. The airlines says that's not true.

The pilots have voted to authorize a strike. But a walkout does not seem imminent.

A spokesperson for the Minneapolis-St. Paul International Airport says Sun Country has not expressed interest in ending its airport leases, one of which runs through 2029.

"Our hope remains that the airline and its pilots can reach an agreement acceptable to all," said airport spokesperson Patrick Hogan. "Should Sun Country request to end its hangar leases early, the Metropolitan Airports Commission will weigh its legal options at that time."