Taiwan is protesting against a move by Singapore Airlines (SIA) and budget carrier Scoot to name the island as part of China on their websites, in an apparent switch to comply with Beijing's recent demand to foreign airlines.
Taiwan representative in Singapore, Mr Francis Liang, told The Straits Times that his office has lodged a complaint with SIA and Scoot over the carriers' "unreasonable" move to change Taiwan's designation on their websites to "Taiwan, China".
He noted that most Taiwanese travel on SIA and Scoot to visit Singapore, and they "would not be happy" to be confronted with Taiwan's new designation.
China's aviation regulator in April gave dozens of airlines a May 25 deadline to remove references on their websites and in other material that suggest Taiwan, Hong Kong and Macau are countries independent of China.
Beijing later extended the deadline to late June.
While the White House has described the order as "Orwellian nonsense" and Taiwan has repeatedly condemned it as "bullying", several airlines have already made the change.
They include Air Canada, Air France, Germany's Lufthansa, British Airways, and Emirates of the United Arab Emirates.
Contacted by The Straits Times, SIA said it amended its website on June 11 in accordance with the Chinese regulator's request.
"As you know, we had received a formal letter from the Civil Aviation Administration of China, and the changes were made in response to the request," a spokesman said.
Relations between Taiwan and China, which have been governed separately since 1949 after a civil war, have deteriorated under Taiwan President Tsai Ing-wen, whose Democratic Progressive Party advocates eventual independence from the mainland.
Ms Tsai on Wednesday denounced China for exerting pressure on international airlines to name Taiwan as part of its territory.
In a meeting at the presidential office in Taipei with Mr James Moriarty, chairman of the American Institute in Taiwan (AIT), Ms Tsai said Washington's opposition to China's airline gambit assures the Taiwanese people they have the support of the United States.
AIT is the US' de facto embassy in Taiwan in the absence of formal diplomatic ties.
Last week, the Financial Times said, citing five people familiar with the issue, that US officials had asked American airlines, including United, American Airlines, and Delta, not to comply with China's demand to write "Taiwan, China" instead of "Taiwan" on their websites and maps.
As of Wednesday, the three US carriers have not made the switch on their websites. Neither have Japan's Japan Airlines and All Nippon Airways.
The US recognises Beijing as the legitimate government of all of China, but has longstanding ties with Taiwan and is bound by its Taiwan Relations Act to protect the island.
Under President Donald Trump, the US has been more vocal about maintaining official and civil exchanges with Taiwan while not rocking the boat too much to avoid Beijing's ire.
Washington sent only a relatively low ranking official from the State Department to the unveiling of the AIT new complex in Taipei on Tuesday.
Japan, which ruled Taiwan for 50 years until 1945 and retains much influence over the island, also remains a staunch ally despite not having official ties with Taipei.
Australia's Qantas Airways said earlier this month it would abide by Beijing's rules but the tweak was being delayed by technical "complexity". Deputy Prime Minister Michael McCormack and Foreign Minister Julie Bishop both accused China of applying undue pressure on the national flag carrier.
Additional reporting by Karamjit Kaur