United Airlines is preparing to place an order for 10 of Boeing Co.’s largest twin-engine jetliners to replace older aircraft plying its longest routes, said people familiar with its plans.

The Boeing 777-300ERs would be the first of that variant bought by United, the world’s second-largest carrier, said three of the people, who aren’t authorized to speak publicly because talks are private. The deal would have a value of $3.3 billion based on list prices, though airlines commonly get discounts.

By buying now, Chicago-based United might be able to drive a bargain as Boeing seeks orders to keep its Everett, Washington assembly line humming until a revamped, larger 777 model debuts in 2020. Boeing garnered 63 orders for its best-selling wide- body jet last year, a pace it will need to maintain to avoid cutting production rates later this decade.

The 777 deal could be announced as early as this week, said two of the people. Luke Punzenberger, a United spokesman, and Doug Alder, a spokesman for Chicago-based Boeing, declined to comment on the potential order.

While United was Boeing’s first 777 customer in 1995, the Chicago-based carrier hadn’t upgraded its fleet with later models, focusing instead on next-generation aircraft such as Boeing’s 787 Dreamliner and Airbus Group NV’s A350-1000 that is coming in a few years.

The -300ER is the top-selling of Boeing’s 777 models, popular for its operating efficiency and large cargo hold.

The jetliner seats 386 people in a typical three-cabin layout and can fly 7,825 nautical miles — about 500 miles farther than the four-engine Boeing 747 jumbos that United flies across the Pacific.

United also holds orders for 35 A350-1000 jetliners, an Airbus model sized to directly compete with the largest 777.

Toulouse, France-based Airbus said this month it would aim to squeeze 20 more seats into the jet for a total of 389 in a bid to boost sales. The A350-1000 order tally shrank by 20 in 2014 to a total of 169, according to Airbus’s website.

–With assistance from Richard Clough in New York.

This article was written by Julie Johnsson and Michael Sasso from Bloomberg and was legally licensed through the NewsCred publisher network.

Photo Credit: A United 777-200ER aircraft. United Airlines