Bombardier has concluded a firm purchase agreement with India’s SpiceJet for up to 50 Q400 turboprops, making it the largest single order ever for the Q400 and bringing total Q400 firm orders to over 600 aircraft. SpiceJet will become the first in the world to operate a 90-seat turboprop, pending certification by regulatory authorities.

The two companies had signed a Letter of Intent at the Paris Air Show in June.

The purchase agreement includes 25 Q400 turboprops and purchase rights on an additional 25 aircraft. Based on list prices, the order is valued at up to $1.7bn.

Since 2010, SpiceJet has taken delivery of 15 new Q400 aircraft. The airline — which claims to operate India’s largest regional fleet — currently operates 20 Q400 aircraft in a 78-seat configuration to domestic and international destinations. It also operates 35 Boeing 737NGs. Including SpiceJet’s order, Bombardier has recorded firm orders for a total of 610 Q400 aircraft.

The fast-growing Indian carrier has also placed orders for 142 737 MAX aircraft, according to Boeing’s website, and holds purchase rights for a further 50 aircraft.