Boeing 777X to have retractable wings, a first for passenger travel

May 25 (UPI) -- The Federal Aviation Administration has signed off on proposed designs for the newest version of Boeing's 777, which will feature retractable wings.

Boeing said the 777X design will expand the wingspan to 235 feet. That's too wide for most airports, so the tips of the wings can retract and reduce the span to 212 feet -- small enough to continue using terminals designed for older 777s.

The wings won't fold while in flight, only while the plane is on the ground. Engineers have developed primary and secondary latch systems that will keep the wings fully extended during flight.

The standard wingspan is just under 200 feet. By contrast, wings on Boeing's 787 measure 197 feet and 117 feet on its 737.

A wider wingspan boosts fuel-efficiency by lowering drag. The 777X will carry as many as 425 people.

The FAA has approved the design and submitted it to the Federal Register.

"These airplanes will have a novel or unusual design feature when compared to the state of technology envisioned in the airworthiness standards for transport-category airplanes. This design feature is folding wingtips," the FAA said in the filing, which adds special conditions for the new jet to be considered airworthy.

"These special conditions contain the additional safety standards that the [FAA] considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards."

Boeing plans to unveil the 777X, its third version of the jetliner, in 2020.

Folding wings have been featured on military planes, but this would be the first time they are installed on a commercial aircraft.

Retractable wings were a part of the design for Boeing's proposed supersonic transport in the 1960s, but the aircraft was never built.

Boeing's new 777s will have folding wings from CNBC.