The North Central Airlines' route system was again extended to Canada on May 1, 1961, this time from Minot to Regina, Saskatchewan.

This cover was carried on the inaugural Air Mail Route 86 flight from Minot, North Dakota to  Regina, Saskatchewan  (where it was backstamped) and is listed in the Contract Air Mail Flights (CAM) Section of The American Air Mail Catalogue as 86N129.

Effective July 1, 1979, the Civil Aeronautics Board approved the merger of Southern Airways and North Central Airlines. The merged companies became Republic Airlines, Inc.

On January 23, 1986, Northwest Airlines announced the biggest merger in U.S. civil aviation history to that date — an $884 million purchase of Republic Airlines. The two carriers filed a merger application with the Department of Transportation on January 27. The Justice Department opposed the merger because it would “substantially lessen competition” in violation of antitrust laws. Full hearings regarding the merger were held and on July 31 the Department of Transportation approved Northwest Airlines’ takeover of Republic Airlines. On August 12 the acquisition of Republic was completed as officials from both airlines transferred ownership of Republic to Northwest. On October 1, 1986, the operations of Republic were fully integrated with a single Northwest flight schedule.