Air Canada's chief executive is throwing his support behind Bombardier in the airplane maker's battle with Boeing and the U.S. government.

"We are proud to have been an early large customer of Bombardier's CSeries platform," Calin Rovinescu told a business audience at a luncheon in Montreal Thursday. 

"The CSeries is simply the best in class for its size, and we see it comfortably coexisting in our fleet."

Air Canada became a high-profile CSeries customer last year, when it signed a firm order for 45 CS300 jets, with options to buy 30 more of the planes. 

Bombardier's new aircraft has sparked a cross-border battle after the U.S. Commerce Department sided with Boeing in its complaint that CSeries jets are being priced at "absurdly" low levels.

"We find the preliminary decision of the U.S. Commerce Department imposing duties of nearly 220 per cent extremely troubling," Rovinescu said, "As it has the effect of potentially stifling both innovation and competitiveness to the detriment of both airlines and passengers."

He saluted Bombardier for providing an option for a segment of the aviation market - small narrow-body aircraft - that he deems underserved, and expressed disappointment in Boeing's "attack."

Rovinescu's words of support for Bombardier come on the heels of a ringing endorsement from another CSeries customer.

Air Baltic CEO Martin Gauss told BNN Thursday his company is going to buy 14 more of the jets, and said there are signs of rising demand for the CSeries among other airlines.