MENDOTA HEIGHTS — The chairman of Sun Country Airlines is threatening to ground its planes during a pay dispute with the 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.”

Minnesota Public Radio,reports the company declined to comment. The pilots union dismissed the letter as a bargaining tactic.

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.