United Parcel Service (UPS) pilots want the right to refuse to fly to Hong Kong, further threatening to undermine the world's biggest air cargo hub, days after FedEx Express aircrew called for the suspension of flights to the city.
The Independent Pilots Association (IPA), which represents the global freight carrier's cockpit crew, wants the US company to only use volunteer staff to fly to Hong Kong, which is battling a surge in Covid-19 infections.
There is already an agreement with the airline covering flights to mainland China, which has been in place since February.
On Wednesday, FedEx pilots called on the company to halt Hong Kong flights, which they said posed an "unacceptable risk". Their anger stemmed from the forced hospitalisation, and poor quarantine conditions, three company pilots were subjected to after testing positive for the virus on arrival in the city.
The IPA said its agreement with UPS allowed pilots and its members to "opt into" and volunteer to operate mainland China flights.
"The IPA has requested that UPS use the same volunteer system for Hong Kong. The company has not responded yet," Brian Gaudet, the association's communications director, said.
Hong Kong is battling its most serious outbreak of the virus. A record 149 cases were reported on Thursday, the ninth straight day of three-figure increases, pushing the city's total to 3,151, with 25 related deaths.
The United States has been the worst hit by the virus. It had recorded more than 4.46 million cases and more than 151,000 deaths as of Thursday.
UPS, whose main operating base in Louisville, Kentucky, is the fourth busiest air freight hub in the world, said it did not talk publicly about discussions with its pilots' union.
Mike Mangeot, the cargo airline's strategic communications director, said it had "coordinated extensively" with its pilots to ensure their safety and the continuity of its operations, which included opt outs of mainland China flights "if they did not feel safe in doing so due to coronavirus concerns".
He added: "Our public affairs team has also worked at length with government agencies around the world, including in China and Hong Kong, to keep our employees safe and our customers' shipments moving on time."
Shenzhen is the main East Asia hub for UPS, handling an average of 14 company flights per day, flying across the region and to the rest of the world.
Hong Kong handles about 10 UPS flights a day focusing on Asia to Europe and vice versa. The airline operates 265 aircraft and charters a further 296, mounting 2,300 flights per day.
UPS had six scheduled flights on Thursday, but four were cancelled. FedEx also had six flights, which departed as normal. The Cathay Pacific Group, the fifth largest cargo carrier in the world, had a combined 29 flights scheduled to take-off.
Mangeot said the cancellations were "normal variations in the network" and the company was "in good shape crewing our flights".
FedEx reiterated an earlier statement it made in response to calls for it to suspend flights to Hong Kong, and there had been no apparent changes made to its flight network.
"Our operations in Asia-Pacific are vital to our global network, and we are proud of the way our entire FedEx team has continued to operate through difficult circumstances to keep the global supply chain moving around the world," it said.
Increased measures by the government, which took effect on Wednesday, require aircrew to be tested before they fly to Hong Kong. They are also banned from taking public transport to avoid mixing with the general public, and must self-isolate in hotel rooms.
Between July 8 and July 28, 18 aircrew tested positive for the virus, and of those, eight were pilots. Since July 8, all aircrew were required to be tested upon arrival at Hong Kong.
Earlier this week, the Hong Kong government said that it recognised the impact testing would have in the industry, but it considered it "necessary to adopt stringent measures at this time".