United Airlines is saying goodbye to its fleet of Boeing 747s sooner than expected.

Scott Kirby, president, United Airlines, confirmed the Chicago-based carrier will operate its final Boeing 747 flight in the fourth quarter of 2017. The initial plans to phase out the 374-seat aircraft was set for the end of 2018.

“As deeply connected as we all are to this iconic aircraft, the time has come to retire our 747 fleet from scheduled service,” said Kirby. “It’s a bittersweet milestone. Today, there are more fuel-efficient, cost-effective and reliable wide-body aircraft that provide an updated in-flight experience for our customers traveling on long-haul flights.”

Pilots and crewmembers of the 747s are ensured of a smooth transition along with a memorable retirement celebration for the aircraft.

Plans to accelerate the retirement comes the same time the Federal Aviation Administration is expected to issue a directive calling for potentially expensive fixes to older jet models.

United will replace the aircraft with Boeing 777-300ER models that seat eight fewer passengers than their predecessors, now seating 366 travelers. The airline also plans to add more Boeing 787-9 Dreamliner models, capable of seating 219 and 252 passengers.

Delta Air Lines, the only other U.S. airline currently using the 747s for passenger service, is also retiring the fleet by the end of 2017.