Air China Ltd said it and wholly-owned unit Air China Import and Export Co have jointly signed an agreement to buy 45 aeroplanes from Boeing Co.
In a statement filed with the Shanghai Stock Exchange, the company said the order breaks down into 15 Boeing 777s and 30 Boeing 737s.
The airlines did not give a value for the contract but added that it will obtain a price lower than the combined catalogue value of $6.3 billion.
The aircraft will be delivered between 2011 and 2015, the company said, adding that its fleet capacity is expected to rise by 35 percent from 2007 levels after the deal.
Last week, the company won approval from the securities regulator to issue up to 400 million additional shares to help finance aircraft orders.