Taiwan says it's a democratic, self-ruled country in East Asia. China disagrees.

Under the "One China" policy, Beijing considers Taiwan to be a province of China, one that will eventually be fully reunified — by force, if necessary. China is adamant about this and frequently seeks to assert its claim to Taiwan on the global stage.

In order to prevent international recognition of Taiwan as a country — which could diminish China's claim to it — the government even demands countries with which it has diplomatic ties to cut relations with Taiwan.

And now China has set its sights on a new target: foreign airlines.

On April 25, the Civil Aviation Administration (CAA) of China ordered a number of international airlines, including several from the US, to change how Taiwan is described on their websites and promotional material.

The US State Department confirmed to Business Insider airlines received the letter and said it had raised "strong concerns" with Chinese authorities in Beijing about the order.

"Regarding websites, we object to Beijing dictating how U.S. firms, including airlines, organize their websites for ease of consumer use. Chinese companies’ websites operate freely and without political interference in the United States," a State Department official told Business Insider.

The agency also said it "will consider taking appropriate action if necessary in response to unfair Chinese actions."

But this is not the first time China has tried to exert its influence over foreign companies. Earlier this year, the hotel chain Marriott was forced to shut down the Chinese version of its website for a week. The fast-fashion retailer, Zara, was ordered to complete a "self-inspection" and turn in a rectification report for listing certain areas as countries. China's territorial claims to Taiwan have gradually become a confusing and diplomatically-fraught issue for foreign companies, and now air carriers. Keep scrolling to see how major airlines are dealing with China's attempts to get foreign countries to comply with its view that Taiwan is part of China: