THE HAGUE, April 30 -- Air France-KLM agreed a deal for the maintenance of Air China's Boeing 777 fleet for a period of 15 years, the Franco-Dutch airline announced on Wednesday.

In a statement, Air France-KLM called the contract "the most important agreement in its history in terms of maintenance."

The specialist maintenance division of the group agreed to maintain the GE90 engines powering Air China's fleet of Boeing 777s.

The deal is said to be part of a wider cooperation in the field of aircraft maintenance with Air China, which operates 20 777-300ER aircraft and eight 777-200 freighters as part of its joint venture with Air China Cargo. No financial details were disclosed so far.

"This agreement illustrates our ability to expand in a highly competitive sector," said Air France-KLM CEO Alexandre de Juniac in a press release.

"It is an additional success story for our maintenance division and positive for employment in a growing sector within the group and confirms our development strategy," he added.