India's budget airline IndiGo on Monday said it had finalized a deal to purchase 250 single-aisle aircraft from Airbus, in what the European manufacturer described as its largest ever order by number of planes."This new order reaffirms IndiGo's commitment to the long-term development of affordable air transportation in India and overseas," IndiGo's president Aditya Ghosh said in a statement jointly issued by the Indian airline and Airbus.The value of the order for 250 A320neo planes has not been disclosed. The A320neo has a list price of more than 106.2 million dollars, making the deal worth some 26.55 billion dollars.The provisional order was announced in October but IndiGo said it had signed the deal on India's 69th independence day on Saturday.IndiGo has ordered a total of 530 A320 family aircraft including the latest order.Founded in 2006, IndiGo is India's largest airline with a market share of 33.8 per cent of domestic passenger volume.India's civil aviation sector has seen massive expansion over the past decade and its market has the potential to become the biggest globally by 2030, according to the KPMG consultancy.The number of Indian airline passengers has grown by some 13 per cent annually over the last decade, according to the Airports Authority of India, to 159 million in 2013.Ghosh had earlier said that India was among the most "under-penetrated aircraft markets" in the world - with less than 400 commercial planes for a population of over 1 billion people.IndiGo officials expect the deliveries of the 250 aircraft will commence by 2018.