Bombardier said on Monday its aerospace division has finalized terms on US regional airline Colgan Air's option to buy another 15 of Bombardier's Q400 NextGen turboprop airliners, on top of the 15 firm orders announced in January.

On January 15, Colgan Air ordered 15 of the fuel-efficient, low emission, 70- to 80-seat turboprops for a total of about USD$432 million.

Colgan Air is a subsidiary of Pinnacle Airlines.

Montreal-based Bombardier is the world's third-largest maker of civil aircraft.

Its shares have been under pressure lately, dropping around 20 percent so far this year, as the corporate jet market deteriorates due to the weak economy.