Indian low-cost carrier IndiGo has signed a memorandum of understanding (MoU) to buy 250 A320 neo(new engine option) planes from Airbus, a purchase that could be worth nearly $26 billion and rank as the largest single order of jets from the European plane-maker.

IndiGo has previously placed orders for 100 A320s and 180 A320 neo planes.

IndiGo has a fleet of 83 Airbus A320s and has ordered or taken delivery of 280 Airbus aircraft, including 160 of the upgraded and re-engined A320neo model that will begin arriving next year. It was one of the first customers for the A320neo.

The provisional deal extends Airbus’s lead over Boeing Co in the Indian market and could, if confirmed in coming months, close a worldwide deficit in orders versus its U.S. rival during the first nine months of the year.

IndGo is expanding aggressively as it seeks to win more market share in one of the world’s fastest growing aviation markets and cement its position as the country’s only profitable carrier.