Air China Ltd, the nation's biggest carrier by market value, agreed to buy two Boeing Co 747-8 aircraft in the airplane maker's first sale of the models this year.

Air China will also purchase one wide-body 777-300 plane, 20 single-aisle 737-800 jets and eight 777 freighters, according to a statement over the weekend. The planes have a combined catalog value of $4.8 billion. Boeing granted "significant price concessions" through credit agreements, the airline said in the statement.

Boeing, based in Chicago, hasn't sold more than five 747-8 aircraft a year since Deutsche Lufthansa AG purchased 19 of the planes in 2006, and concern that persistently weak demand could prompt the company to curtail production has been mounting.