United Airlines said a Boeing 787 Dreamliner en route to Tokyo made an emergency landing in Seattle, marking yet another hiccup that has plagued the fleet since January.

When the Dreamliner plane en route from Denver International Airport to Tokyo reached the Pacific Ocean off Vancouver Island Tuesday something went awry with an oil filter in one of its engines, United said in a statement.

"United flight 139 from Denver to Tokyo-Narita diverted to Seattle due to an indication of a problem with an oil filter. The aircraft landed normally and without incident and we are working to re-accommodate customers," United said.

Boeing said they're aware of the emergency landing and "engaged with United to provide any support required." The engine is made by General Electric and Boeing says it's "coordinating" with them on the issue.

The emergency landing is yet another problem that has beleaguered Boeing's Dreamliner fleet, which was grounded worldwide in January due to recurring issues with smoldering lithium ion batteries. The entire fleet of about 50 planes was grounded until April.

Engineers had spent 200,000 hours analyzing what caused the batteries on two of its flights to overheat in January. Boeing engineers developed layers of additional safety measures to eliminate the risk of fire from the faulty battery system.

United is the only U.S. carrier currently flying the Boeing 787s, which has been touted as the plane of future.

Joshua Trujillo/AP Photo