It issued an order Tuesday requiring Cathay Pacific to file schedules for all US flights within seven days to determine if any are "contrary to applicable law or adversely affect the public interest."

Hong Kong in January issued new rules requiring locally-based air crews to observe quarantine when returning, but exempted flights between here and Anchorage, Alaska's biggest city.

The order was issued in reaction to Hong Kong's quarantine restrictions that exclusively benefit Hong Kong carriers and "impaired the operating rights of US carriers," it said.

While FedEx's Hong Kong-based crews serve only intra-Asia routes and so do not benefit from the Anchorage exception, it said, Cathay Pacific operates a large transshipment operation at Anchorage.

"This carveout effectively provides Cathay Pacific with the ability to continue those operations without impact," it said.

The order also applies to Hong Kong Airlines and Hong Kong Express, but they are not currently operating US flights.

As a result of the quarantine rules, FedEx is incurring "significant operational costs and personal burden on its Hong Kong crew members," it said.

FedEx had temporarily relocated its Hong Kong-based crews to San Francisco "in order to maintain the viability of critical operations in its intra-Asia network."

On Tuesday, a FedEx spokesman said it hoped the department's order "will aid in resolving this matter" and added it was working with US and Hong Kong authorities and the Air Line Pilots Association "to address Hong Kong's entry and quarantine requirements for locally-based crew members."

In a previously unreported February 26 letter, the department urged Hong Kong authorities "to restore the level playing field in the US-Hong Kong market; otherwise, the department may have no choice but to consider regulatory action."