MONTREAL - Bombardier says Latvian flag carrier Air Baltic has converted its remaining seven option aircraft for the CS300 aircraft to a firm order.

This brings Air Baltic's total firm order to 20 planes under an agreement initially signed in December 2012.

Based on the list price of the CS300, Bombardier says this firm order is worth about US$506 million.

Bombardier says the Riga-based airline will be the first customer in the world to operate the CS300 when it takes delivery in the second half of 2016.

Air Baltic, which began flights in 1995, already operates a dozen of Bombardier's Q400 aircraft. CEO Martin Gauss says the new CS300 aircraft will help the airline improve its connections to Western Europe and the Eastern markets.

The Montreal-based transportation giant says it has booked orders and commitments for 678 C Series aircraft, which include firm orders for 250.