FedEx Corp. tumbled the most in nearly six weeks as President Donald Trump ordered tariffs on at least $50 billion in Chinese imports.

FedEx, which operates the world’s largest cargo airline, has a bigger presence in Asia and China than United Parcel Service Inc., having gained a major foothold through its 1989 acquisition of Tiger International Inc. The Memphis, Tennessee-based courier also has a larger international air network than its rival.

“It’s definitely the tariffs on China impacting” FedEx shares, said Kevin Sterling, a Seaport Global Holdings analyst. “If global trade does contract, they’re going to feel it.” FedEx in January opened an air-cargo hub in Shanghai to handle growing cross-border transactions.

Trump’s order sparked a broad market rout on concerns that the levies would trigger a trade war and hurt the broadest global economic recovery in years. FedEx Chief Executive Officer Fred Smith on Tuesday warned that the tariffs could threaten U.S. economic health.

“The better approach is to encourage open markets and free exchange of products and services and to reduce barriers to trade,” Smith said on a conference call to discuss quarterly earnings.

FedEx fell 3.8 percent to $239.61 at 2:22 p.m. Thursday in New York, after declining as much as 5.2 percent, the most since Feb. 9. UPS slipped 1.8 percent.

Results for FedEx’s fiscal third quarter also may have weighed on the shares, said Lee Klaskow, a Bloomberg Intelligence analyst. While the courier’s Freight and Ground operations performed well, “there were some concerns” regarding its Express airline unit, the largest at the company, he said.

U.S. Trade Representative Robert Lighthizer within 15 days will propose a list of products that will carry higher tariffs.