Sun Country Airlines plans to open a pilot base in Portland, Ore., that would be the company’s first ever outside Minneapolis-St. Paul, but the airline first must negotiate terms with the union.

The Eagan-based airline on Tuesday notified its pilots’ union, the Air Line Pilots Association International (ALPA), that it wants to discuss the plan with them. While the union can’t dictate where the company opens new bases, there’s a provision in the pilots’ five-year contract, signed in 2015, that forbids the airline from opening a base without the union’s approval of the terms.

“We look forward to productive negotiations with the company on how best to create this new domicile,” the airline union’s Master Executive Council said in a statement.

A base, or domicile as it is called in the industry, is where a pilot begins or ends all his or her work trips. It’s common for U.S. airlines to have several domiciles scattered across the country, but Sun Country hasn’t had a need for a second one until recently.

Sun Country’s interest in opening a second pilot base reflects the airline’s growing route network outside the Twin Cities. It is beefing up flight service in Portland, Dallas-Fort Worth, Nashville and several other cities.

While some airlines allow pilots to live in a city other than where they domicile, such an arrangement requires unpaid commuting time between the pilot’s home and their base, before and after their scheduled work trips.

Sun Country has already opened new bases for flight attendants, a unionized group that doesn’t have the same contract provisions as the pilots. In December, Sun Country opened a 25-person flight attendant base in Dallas-Fort Worth and, on March 2, it will open a 38-person flight attendant base in Portland. The company also recently decided to open a flight attendant base in Las Vegas for about 35 to 40 crew members.

Several flight attendants relocated from Minneapolis-St. Paul, but a company spokeswoman said the majority have been new hires.

Sun Country’s operations have, at times, been strained by a workforce concentrated in the Twin Cities, executives have said. For instance, if a weather event delays flights and crews here, it can create a ripple effect across the airline’s entire network.

The company declined to say how big the Portland base might be, but a notice sent out by the union said the company wants it to open in July. The Sun Country pilots negotiating committee is scheduled to have its first meeting with management on Monday to begin negotiations.

If the plan proceeds, the most senior pilots will have first choice on basing in Portland or the Twin Cities through what’s called a vacancy bid. If not enough pilots choose Portland, the company will backfill with the least senior members. The union said it’s too early to know what effect this may have on the pilot group.

Sun Country, like many other U.S. airlines, is facing a pilot shortage. The company is hiring and training new pilots but not fast enough to meet demand. Last year, it developed a program with Minnesota State University-Mankato and the University of North Dakota that gives flight students a guaranteed pilot job after they graduate and log enough flight hours.