BEIJING, July 11 (Xinhua) -- China's national flag carrier Air China signed agreement Thursday to buy 20 A350-900 planes from global aircraft producer Airbus to improve its transport capability.

The deal is worth about 6.537 billion U.S. dollars based on open market prices registered in January 2018, and the actual sum will be adjusted later and paid in instalments, Air China said in a statement disclosed on the Shanghai Stock Exchange.

Deliveries of the jets will be conducted in a phased manner from 2020 to 2022.

The deal is expected to enhance Air China group's transport capability by about 9.7 percent, according to the statement.

As one of the largest airline in China, the group had 669 airliners by the end of 2018.