Which airline introduced the Airbus A220 into commercial service?

Swiss Global Air Lines introduced the Airbus A220 into commercial service.

The aircraft entered airline service in July 2016 under its original CSeries identity, as the CS100. Swiss Global Air Lines, a subsidiary of the Lufthansa Group, operated the first passenger service from Zurich to Paris. Airbus later acquired a majority stake in the program and renamed the aircraft family A220.

The CS100 became the A220-100, while the larger CS300 became the A220-300. This change explains why older references identify Swiss as the first operator of the Bombardier CSeries rather than the Airbus A220.

Air Baltic later became an important A220 operator, and Delta Air Lines became a major North American customer. Neither, however, introduced the aircraft into commercial service. The A220 was designed for efficient operation on smaller narrow-body routes and uses Pratt & Whitney PW1500G geared turbofan engines.