Boeing expects airframe technology will play as crucial a role as new clean-burning engines in developing a replacement for its best-selling 737, providing a potential advantage over Airbus in the race to design the next generation of single-aisle aircraft.

The two rivals are developing replacements for their 737 and A320 families, which are the workhorses of global airline fleets and account for half of the $3,200bn in aircraft deliveries forecast between now and 2025.