Boeing Co. is heading closer toward finalizing a deal with China to sell as many as 500 aircraft, according to people familiar with the matter, a transaction that would end a sales drought that stretches back to US President Donald Trump’s last visit in 2017.

Boeing stock rose more than 2% on the news.

The two sides are still hammering out terms of the complex aircraft sale, including the types and volume of jet models and delivery timetables, according to one of the people, who asked not to be identified discussing confidential matters.

The mega sale to China, years in the making, is contingent on the two nations diffusing the trade hostilities that hark back to Trump’s first term in office — and could still fall apart, they said.

Chinese officials have already started consulting domestic airlines about how many Boeing aircraft they’ll need, the people said. The transaction taking shape is similar in scope to the order for as many as 500 jets that China’s central planners have struck with Airbus SE, but haven’t yet announced, they added.

Complicating matters for Boeing is a leadership void in China. Alvin Liu, its top executive in China and a fluent Mandarin-speaker with extensive government contacts, left the company in recent weeks. Carol Shen has been named interim president of Boeing China, said people familiar with the matter.

Boeing declined to comment on any potential deal or management changes.

Aircraft orders for Boeing have figured large in US diplomacy since Trump returned to the White House in January, with nations touting new, tentative and existing deals for airplanes, which are as expensive as skyscrapers, to narrow trade imbalances with the US.

For China, the deal would secure aircraft delivery slots that are hard to come by at both Boeing and Airbus, which are largely sold out into the 2030s. The world’s second largest’s aviation market is expected to more than double its commercial fleet to 9,755 airplanes over the next 20 years, by Boeing’s estimation, far more than China’s homegrown planemaker Comac could manufacture.

The country’s top economic planning agency, the National Development and Reform Commission, recently sought input from Chinese carriers about how many jets they want, one of the people said. Talks centered on the 737 Max series of aircraft, Boeing’s popular single-aisle jet, in a sign Beijing is laying the groundwork for a major order.

Boeing’s last Chinese deal was unveiled in November 2017 during Trump’s first state visit to China. The deal amounted to orders and commitments for 300 single-aisle and twin-aisle planes valued at $37 billion at the time.

The next year, Boeing’s China deliveries peaked, when a quarter of its jets ended up in the mainland. Airbus has dominated sales and deliveries to China since 2019, when the nation’s regulators were the first to ground the 737 Max after two fatal accidents.

Boeing has notched only 30 orders with Chinese carriers and leasing companies since the start of 2019, according to the company’s website. In an interview with Bloomberg in January, Chief Executive Officer Kelly Ortberg was optimistic that years of talks with Beijing would finally pay off.

“We certainly hope that there’s an opportunity for some additional orders in the next year with China,” he said.