The Chinese aircraft leasing company Hong Kong Aviation Capital said on Thursday it had agreed to buy 60 Airbus jetliners in a deal worth up to $6.3 billion (4.7 billion euros). HKAC chief executive Donal Boylan has signed a memorandum of understanding (MoU) with Airbus that covers \"the purchase of 40 A320neo and 20 A321neo aircraft,\" a statement said. They are the latest, fuel-efficient versions of Airbus\' best-selling medium-range aircraft, and the total number of planes carries a list price of $6.3 billion, though substantial discounts are the norm for large orders. \"This is our first direct order with any aircraft manufacturer and our first commitment for the A320neo\" Boylan was quoted as saying. HKAC is one of a number of growing aircraft leasing companies which account for a growing percentage of all aircraft purchases, and the size of the deals allows them to negotiate better rates than small airlines. \"We are delighted to have HKAC as our new customer for the Neo, the world\'s best selling single-aisle aircraft,\" Airbus Chief Operating Officer John Leahy said. Alain Guillot, an expert in aerospace and defence at consultants AlixPartners has estimated that between 2007 and 2012, the share of planes belonging to leasing companies has grown by 20 percent. \"Planes being rented out represented 35 percent of the worldwide fleet in service in 2012,\" excluding private aircraft, he said. Guillot has also calculated that nearly half of Airbus and Boeing order books are filled with deals done with leasing companies. Airbus has indicated that sales via leasing will make it easier for many airlines to operate its A380 superjumbo airliner.