HONG KONG - Air China, the country's leading carrier, said late Thursday that it would pay $4.5 billion to buy 20 Airbus planes.

In a statement filed to the Hong Kong Stock Exchange, the Beijing-based carrier said Air China and its import agent AIE had entered into the agreement with Airbus to purchase 10 Airbus 330-series aircrafts and 10 Airbus 350-series aircrafts.

The aircraft price is subject to price escalation by applying a formula. Airbus has granted to Air China significant price concessions with regard to the Airbus planes, according to the statement.

Air China is expecting to take delivery of 10 Airbus 330-series aircrafts in stages from 2013 to 2015 and 10 Airbus 350-series in stages from 2018 to 2020, it said.

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The deal will be funded through cash generated from the airline's business operations, commercial bank loans and other financing instruments, according to the statement.

Air China also said the purchasing will increase its fleet capacity by about 18.6 percent based on available ton kilometers by the end of last year.

Air China operates domestic, regional and international services, which fly to more than 120 destinations. It operates a total fleet of more than 260 Airbus and Boeing jet aircrafts, the airline said on its website.

Air China has ordered more than 200 Airbus and Boeing planes so far. In 2009, Air China carried 41.3 million passengers.