Sun Country Airlines in March will stop transporting mail for the U.S. Postal Service to focus its resources on its faster growing businesses.

The Minneapolis-based leisure carrier's business with USPS has been declining and becoming less profitable. The share of its operations devoted to carrying mail is tiny at just 0.1% of the company's overall revenue, said Greg Mays, the airline's chief operating officer.

"We've grown [our]business pretty significantly over the years so it's a smaller and smaller percentage of total revenues," Mays said.

It also reflects a shift in strategy by the federal postal service. In an email, Sue Brennan, a spokeswoman for the agency, said it has been moving higher volumes of mail through its surface — or land transportation — network as part of a plan for the postal service to be self-sustaining.

The 17 Sun Country employees involved in postal service mail transport will be moved into other roles as the airline focuses on its three core businesses: scheduled airline service, charters and cargo, particularly for Amazon.

Sun Country has a workforce of nearly 2,500.

March 3 will be Sun Country's last day transporting USPS mail and freight.

In November, Sun Country announced a major expansion of its commercial network, with more than a dozen new nonstop routes from Minneapolis-St. Paul International Airport this year, including to Atlantic City, Colorado Springs, Louisville and New York. Including those routes, Sun Country operates 120 routes serving more than 90 airports.

During the pandemic, the low-cost airline relied more heavily on cargo and charter flights to offset the steep revenue drop in its passenger service. The carrier balances its scheduled passenger service with its charter and cargo operations.

In 2019, Amazon signed Sun Country to a six-year cargo contract. And in 2021, the airline signed a five-year charter agreement with Major League Soccer teams, including Minnesota United. Sun Country also provides charter service for Caesars Entertainment.