"The CAAC's intention could be to inform people to board the plane with the form of ID used in making the booking. Something may have gone wrong when it sent out directives to the airports, which has created misunderstandings," said Li Xiaojin, a professor of aviation economics at Civil Aviation University of China in Tianjin.

Under the circumstances, the authority needs to explain to the public and airports as soon as possible to make things right, Li said. "Also, it needs to educate the public about changes in check-in policies, with explanations well in advance, because it will affect so many people."

According to the civil aviation safety inspection rules, which were passed by the CAAC and took effect on Jan 1, a passport is a valid travel document for domestic flights - contradicting the short-lived rule.

Many people complained on social media.

"It took more than 15 days for the CAAC to clarify the situation, which has confused and affected many passengers. I don't think it is acceptable," said Xiong Tiantian, 30, who was scheduled to fly from Beijing to Auckland, New Zealand, via Guangzhou on Wednesday.

She said she called the customer service hotlines at Beijing Capital and Guangzhou Baiyun International airports on Sunday to inquire about the new rule.

"I was confused and a bit shocked when I found out that the two airports have two different policies," she said. "I've decided to travel with my ID card just in case something changes during my holiday."