Less than a year ago, executives from FedEx and UPS were talking about how they were handling a flood of packages from China to American consumers.

“Explosive” is how Carol Tomé, UPS’s chief executive, in July described the volume of shipments from e-commerce companies selling Chinese goods in the United States. And FedEx’s chief customer officer, Brie Carere, said about those companies in June, “No one carrier can serve their entire needs.”

But that torrent is expected to slow to a trickle after President Trump on Friday closed a loophole that had allowed cheap goods from China to enter the United States without paying tariffs.

The business of transporting hundreds of millions of low-value shipments on as many as 60 freighter flights a day between China and the United States could now wither.

A falloff in such shipments could deprive companies like UPS, FedEx and DHL of a big source of revenue. Airlines, mainly those that carry only cargo, and smaller logistics companies could also suffer. Passenger airlines may also be hurt somewhat because they carry some of those packages, too.

UPS said last week that it expected the revenue from shipping packages from China to the United States — its most profitable trade lane — to decline roughly 25 percent in the second quarter of this year, from a year earlier. UPS also announced that it would cut 20,000 jobs this year as part of a long-term plan to reduce costs, and said “macroeconomic uncertainty” prevented it from updating its forecasts for revenue and profits for 2025.