Plane maker Bombardier Inc is close to sealing an order from a Chinese lessor for its CSeries aircraft.

Any such deal would signal increasing interest in Bombardier's biggest-ever jet.

Bombardier declined to identify the prospective buyer, but Fred Cromer, its president for commercial aircraft, said at the ongoing Aviation Expo China 2015 in Beijing that the company is "in the process" of firming up earlier conditional deals and talking to new customers.