On Friday, the Civil Aviation Administration of China asked Delta to investigate the listing of Taiwan and Tibet as countries on its website, and called for an "immediate and public" apology.
The aviation authority also said it would require all foreign airlines operating routes to China to conduct comprehensive investigations of their websites, apps and customer-related information and "strictly comply with China's laws and regulations to prevent a similar thing from happening".
In a statement, Delta apologized for making "an inadvertent error with no business or political intention", saying it recognised the seriousness of the issue and had taken steps to resolve it.
Separately, the same regulator that penalized Marriott - the Shanghai branch of the state cyberspace administration - accused Zara of placing Taiwan in a pull-down list of countries on its Chinese website.
Medtronic had also put "Republic of China (Taiwan)" on one of its websites, the office said in a WeChat post, giving both companies until 6 pm local time to apologise.
Medtronic issued an apology via social media, saying it had updated the website. An executive who answered the phone at Zara's Shanghai office was not able to immediately comment.