Sun Country Airlines began changing over to a new technology system Tuesday, replacing an outdated one that contributed to customer-service problems.

Executives who arrived at the Eagan-based airline in 2017 have bemoaned Sun Country's website and reservations systems, saying the outdated systems hurt the airline with customers and against competitors.

New technology infrastructure built by Minneapolis-based Navitaire will allow Sun Country to implement self-service ticket kiosks at airports, assign seats at the time of booking and give customers more control and options online.

Indeed, the change touches nearly everything it takes to run the airline, including its website, reservations system, travel-agent portals, loyalty-program access and the system used to process and board passengers onto the aircraft.

The transition started early Tuesday morning with the disabling of online check-ins on its website. It notified customers traveling Tuesday that they would need to check-in at airports instead.

Fourteen flights were to be operating during the transition Tuesday evening. All its airports were prepared to do manual check-in and passenger counting during the transition, but executives expected little effect on customers. Sun Country expected the bulk of the changeover to be finished around 4 a.m. Wednesday.

Sun Country Chief Executive Jude Bricker said in December that the airline is spending $6 million on the technology overhaul.

Bricker, who took the helm in the summer of 2017, said it became apparent early on in his tenure that its technology was holding the company back. Under his leadership, the airline has implemented a new ultra-low-cost carrier model that reduces the base fares and lets customers add back the services and amenities they want, for a fee.

Sun Country is also rapidly expanding its seasonal network outside of its Minneapolis-St. Paul hub. All of this adds complexities, and the airline's old technology system was not designed for it.

"This is a big part of the new technology rolling out," Bricker said in December, adding that the new system would streamline information and a customer's ability to self-select, so that "everyone getting on the airplane knows exactly what they are getting."

For customers, the biggest change will be the rollout of self-service kiosks. Bricker said Sun Country was one of the largest airlines without them. "It frustrates the customers," he said. "They show up at the airport and want to print their boarding pass — perfectly understandable."

As well, no other airline had the same point-of-sale system as Sun Country. It doesn't integrate with the most commonly used kiosk systems in use at most U.S. airports.

On Monday, Sun Country wouldn't say when customers might expect to see kiosks at Sun Country ticket counters, but Bricker said in December 2018 that they were planning to roll them out by the end of summer 2019. He also said the airline would be building a new, better website and mobile app.

Sun Country currently uses two different technologies, called Sabre and Pacific, to perform different parts of a customer's reservation. This two-system approach slows down the check-in process — typically taking a counter agent four minutes to check in one passenger.

After a customer makes an initial booking, they can't do anything on their own to their reservation, such as change, cancel or apply a weather waiver. This puts enormous pressure on its customer-service agents, who have to manually make every change and do it within two different systems.

On bad-weather days, Sun Country's customer-service queue quickly develops a backlog, leading to more complaints and frustrations. Ticket-counter lines are also exacerbated under this outdated computer system as people have to get in line to verify passports, check bags, or get their seat assignment.

In a February interview with the Star Tribune, Sun Country's chief marketing officer Brian Davis pinned many of the airline's past breakdowns in customer service on the limits of the technology system. "There's definitely a sense of urgency to move as quickly as we can to get the tools in customers' hands in 2019," Davis said.