Air China <601111.SS> <0753.HK> said late on Friday that it would buy 20 Boeing 777-800 airplanes for $1.4 billion.

The planes, which will be delivered between 2013 to 2015, will boost Air China's fleet capacity by about 5 percent from December 2009, based on available metric ton kilometers, allowing it to increase the frequency of flights, the carrier said in a statement to the Hong Kong stock exchange.

The airline said it would pay for the planes with cash, bank loans and other financing tools.

Chinese airlines are benefiting from solid air traffic growth in China, which may overtake Japan as the world's second-largest economy this year, industry analysts said.

(Reporting by Sui-Lee Wee, Editing by Jonathan Hopfner)