Richard Branson says Virgin Atlantic will aim to avoid buying four-engined airplanes in future for both economic and environmental reasons, Reuters reports. Virgin Atlantic’s fleet of 38 planes all have four engines, and it has six four-engined Airbus A380 superjumbos on order.

But in April the airline announced it was buying 15 of Boeing’s new fuel-efficient 787 Dreamliner jets with 2 engines.

Virgin is developing biofuels for aircraft alongside Boeing and engine-maker GE Aviation and plans to test them next year.