FARNBOROUGH — Latvian carrier Air Baltic signed a letter of intent (LOI) here for 10 Bombardier CS300 aircraft plus purchase rights for 10 more of the type, in an order aimed at replacing some older, leased Boeing 737s set for retirement.

Air Baltic flies 15 737s today — nine -300s and six -500s — and the 120-seat -500s are, on average, more than 17 years old, according to the Aviation Week Intelligence Network Fleets database. Air Baltic says the 130-seat CSeries aircraft will complement its existing fleet of eight Bombardier Q400 turboprops, while replacing some of the -300 and -500 737s it now operates.

Bombardier says the order is worth $764 million at list prices, growing to $1.57 billion if all purchase rights are exercised.

“We do not align orders with air shows, but when the timing works out, we do,” says Mike Arcamone, president of Bombardier Commercial Aircraft.

With the Air Baltic LOI, Bombardier has 342 CSeries orders, 138 of which are firm.

Air Baltic is in talks with Bombardier for a CSeries simulator at its Riga, Latvia training facility, CEO Martin Gauss says.

Air Baltic will pay for the initial deposits and other “early costs” with cash from operations, says Gauss. Talks with banks and other entities for financing are underway, he adds.

The CS100 is expected to enter service by the end of this year, while the CS300 is expected to follow in 2013.