The budget arm of Indonesian flag carrier Garuda said Thursday it has ordered 25 turboprop planes from Europe\'s ATR, as it looks to tap the nation\'s booming aviation sector in a deal worth about $500 million. \"We\'ve ordered 25 ATR 72-600s with an option to either lease or buy another 25 in 2015,\" said Arif Wibowo, CEO of Citilink. \"With these new propellers, we want to penetrate remote regions and provincial cities which have constraints on their runways.\" The turboprops come with a price tag of more than $20 million each, which could push the order to $1 billion. Indonesians rely on air travel in the sprawling archipelago of more than 17,000 islands and the nation\'s airlines are making some of the world\'s most significant aircraft orders as its growing middle class fuels an aviation boom. In November 2011 Lion Air, Indonesia\'s largest privately-held carrier, unveiled the world\'s biggest commercial aircraft order as it said it would buy 230 Boeing planes worth more than $20 billion. \"The growth of the middle class is very high here and travelling needs are higher,\" Citilink marketing and communications vice president Aristo Kristandyo said. ATR, a French-Italian joint venture based in Tolouse, France, booked an order for 36 planes with Malaysia Airlines last month worth more than $900 million. Citilink is expected to receive the first five planes in September and the rest are due to be delivered by 2017, Wibowo said, adding that a contract would be finalised by the end of the month. The airline has 21 planes, including Airbus A320s and Boeing 737s, serving 11 cities in the country of 240 million people. It expects to service more cities this year, Kristandyo said.