SEATTLE — Boeing’s next big jet may actually spread its wings as it prepares for takeoff.

For the immense wings planned for the 777X, engineers at Boeing Co. are studying a design in which the wingtips fold upward to reduce the jet’s span when it sits at the gate or rolls along a taxiway.

Passengers looking out the 777X’s window would see each wingtip smoothly unfold to the horizontal as the jet lines up for takeoff on the runway.

Just as the hump on a 747 gives that Boeing jet a distinctive look, the folding wingtips would make the next version of the best-selling, twin-aisle 777 instantly recognizable to the general public.

“There’s a coolness factor. … It’s sort of a sci-fi-like thing,” said a veteran Boeing engineer, who is not authorized to speak publicly on the subject. “But to those in the industry, it’s not so surprising.”

The engineer emphasized that the precise design of the 777X won’t be finalized until around 2014, with possible tweaks to design elements even later.

But he said some kind of foldout wingtip looks almost certain, given the very large wingspan Boeing needs to get extra fuel efficiency.

Asked about the possibility of folding wingtips, Boeing spokeswoman Karen Crabtree said the company is still “exploring all technologies” and evaluating the trade-offs they involve.

In fact, it isn’t a new idea. In 1995, Boeing obtained a patent for a folding wingtip design on the original 777, which had a 200-foot wingspan.

That mechanism was even built and tested — the full-scale model used then is on display at the Museum of Flight Restoration Center at Paine Field in Everett, Wash. But no airline ever bought it.

The idea has been revived now because of the oversized wingspan envisaged for the new 777X, the next version of Boeing’s large twinjet widebody.

According to reports in the trade press, engineers are looking at a wingspan as wide as 233 feet — about 9 feet wider than Boeing’s bigger jumbo jet, the 747-8.

Most large airports in the world can accommodate airplanes conforming to an international standard referred to as Code E — which limits the wingspan to 213 feet. Anything wider creates problems.