US regional operator Air Wisconsin is forging a new partnership with American Airlines, opting to end an agreement with its current major airline partner, United Airlines.

Air Wisconsin’s parent company, Harbor Diversified, disclosed the change in a Securities and Exchange Commission filing. Air Wisconsin and American have entered into a five-year purchase agreement that will see the regional carrier operate up to 60 Bombardier CRJ-200 regional jets on behalf of American.

“The capacity purchase agreement currently in effect between Air Wisconsin and United Airlines is expected to terminate in accordance with its terms,” Harbor Diversified said in a statement.

Initially, 40 of the regional jets will be covered by the agreement, with a specified number of aircraft becoming available in March 2023. Up to 20 jets could be added to the agreement, subject to Air Wisconsin satisfying a certain minimum of block utilization thresholds, Harbor explained.

Aviation Week’s Fleet Discovery database shows Air Wisconsin currently has 52 CRJ-200s in service and nine that are parked.

In a memo to employees, American CFO Derek Kerr said the bulk of Air Wisconsin’s operations will focus on American’s hub at Chicago O’Hare international airport, also a hub for American’s rival United.

Data from Aviation Week’s CAPA show for the week of Aug. 22, United has a 45% share of departing frequencies from O’Hare while American has a 35% share.

Kerr noted that presently, American offers 30% more origin and destination pairs than its closest competitors, “and that’s only possible because of the strength of our regional network.”