A long-running labor dispute between Sun Country Airlines and its pilots has shifted into a new gear.

The company's chairman said in an email to a leader of the pilots union this week that Sun Country is in "the process of downsizing the airline, for what will need to be its ultimate shut-down," MPR News reports.

The union sees the remark as a negotiating tactic in a five-year-long contract dispute, MPR says, and an aviation consultant tells the network such warnings from management are not unusual.

Sun Country CEO John Frederickson declined to discuss the contract negotiations with WCCO, but did tell the station: “Nothing that is happening in this process will have any impact on current Sun Country customers.”

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MPR says federal records show Sun Country has been consistently profitable since 2009, while the union says no other airline of its size pays pilots less for flying 737s.

Talks on a new contract have been underway for five years and KSTP reports a mediator has been involved since May of 2012.

The 250 pilots in the union voted in February to authorize a strike but no date for a walkout has been set, according to the Star Tribune.

FOX 9 has the full text of Sun Country Chairman Marty Davis' email to Brian Roseen, who chairs the executive council of the pilots union.

KSTP says Davis' family owns Cambria Holdings of Le Sueur, Minnesota, which purchased Sun Country in 2011, after former owner Tom Petters was charged in a Ponzi scheme.