Air China this week altered its order for 15 Boeing 787 Dreamliners to substitute larger 787-9s for the 787-8s it originally ordered in 2006.

The 787-9 will carry 40 more passengers on average than the 787-8.

Air China will receive the first of the 787-9s in 2015. Originally, the Chinese airline has to be among the first airlines to receive its 787-8s, but it traded those delivery positions with All Nippon Airways for later delivery slots.

The 787 is approaching three years behind its original schedule for its first deliveries. Boeing last week delayed the first deliveries to the first quarter of next year.