The US Transportation Department (DOT) has suspended 44 flights to be operated to the US by Chinese airlines starting Jan. 30 and extending through late March in a direct response to the Civil Aviation Administration of China (CAAC) forcing the temporary suspension of a number of routes to China operated by US airlines.

The 44 flight cancellations imposed by the DOT matches the 44 US airline flights–operated by American Airlines, Delta Air Lines and United Airlines–that the CAAC has canceled.

The source of the dispute between the US and Chinese governments is the CAAC’s rule requiring the suspension of an airline route for two weeks if 5-9 arriving passengers test positive for COVID-19 “after arrival,” or for four weeks if more than 10 passengers test positive.

Starting in late December, the CAAC informed American, Delta and United that the rule had been triggered by positive tests among passengers who were on flights to China. The DOT said the route suspensions were inconsistent with the US-China bilateral air services agreement and give US airlines “undue culpability” because there is no way of knowing when the passengers were infected with COVID-19.

Passengers traveling to China have to show proof of a negative COVID-19 test before boarding their flights. Given that the arriving passengers’ negative tests occurred, in some cases, several days after arrival in China, it is possible some passengers were infected after arriving in China.

The CAAC said it is applying the rule in an even-handed way, noting that under the same rule it has also grounded 42 international flights operated by Chinese airlines.

In its order imposing the 44 flight cancellations on Chinese carriers, the DOT said: “The Chinese government individually clears each and every potential traveler for travel to China prior to their departure from the United States, after verifying pre-departure test results and other required documentation. US carriers, who are following all relevant Chinese regulations with respect to pre-departure and in-flight protocols, should not be penalized if passengers, post-arrival, later test positive for COVID-19.”

The DOT said it “has repeatedly raised its objections with the government of China” over the COVID-19 rule.

The DOT added that it reserved “the right to take such future action as we deem appropriate,” indicating it may be willing to impose additional flight cancellations. The department made clear that its action regarding Chinese airlines was in direct response to the CAAC’s action regarding US airlines.

“We find that the CAAC’s recent actions impairing the operations of Delta, American and United … are adverse to the public interest and warrant proportionate remedial action by the department,” the DOT said. “The CAAC’s unilateral actions against the named US carriers are inconsistent with the provisions of the [US-China air services] agreement and are premised on circumstances wholly outside of the carriers’ control.”

The DOT said it would like to find a solution, stating: “Our overriding goal is not the perpetuation of this situation, but rather an improved environment wherein the carriers of both parties will be able to exercise fully their bilateral rights.”