United Airlines president Scott Kirby said on Wednesday it would accelerate the retirement of its fleet of 20 Boeing 747-400 jumbo jets. Kirby said in a blog post on the company’s United Hub website that its last 747 will fly in the fourth quarter of 2017.

The airline previously planned to retire the 747s by the third quarter of 2018. However, executives said as recently as November that the retirements could be accelerated. United flies 374-seat 747-400s from its San Francisco hub to Beijing, Frankfurt, Hong Kong, Seoul Incheon, Taipei and Tokyo Narita, Flight Global schedules show. “It’s a bittersweet milestone — this jumbo jet with its unmistakable silhouette once represented the state-of-the-art in air travel,” Kirby wrote. “Today, there are more fuel-efficient, cost-effective and reliable wide body aircraft that provide an updated inflight experience for our customers traveling on long-haul flights.”

The airline will take delivery of 12 Boeing 777-300ERs this year, complementing the two that it took before the end of 2016, the Flight Fleets Analyzer shows. It is also scheduled to take delivery of two Boeing 787-9s in 2017. In 2018, United will receive 6 wide body aircraft, including its first three Airbus A350-1000s and first 787-10, the database shows.