In response to the "overpriced" tickets of some airlines after tourists were stranded on the island province of Hainan at the end of the Lunar New Year holiday, an expert said it's natural for the prices of tickets to fluctuate as the demand soars.

"The rise in price of air tickets during the holiday is normal, as most economy-class tickets are sold out, and the remaining tickets for flights departing Hainan are mostly business-class or first-class ones," Li Xiaojin, an aviation economics professor for the Civil Aviation University of China, was quoted as saying by cqnews.net, a Chongqing-based news outlet.

Shipping services in ports of Haikou, capital province of Hainan, were suspended on Wednesday night due to heavy smog, leaving more than 10,000 vehicles waiting in line for ferry services, and also pushing up the prices of air tickets for flights leaving the island.

The business-class tickets of certain flights from Sanya, a popular coastal tourist city, to Harbin, a city in Northeast China, went up to nearly 20,000 yuan ($3,155), sparking controversy over the justification of the price rises.

"Even if it is a headache for passengers to be unable to buy affordable return tickets, based on current information, there is no violation of regulations or laws in the sales of air tickets for flights leaving Hainan by the airlines," said Li.

Ticket information at online travel agency Qunar shows the Saturday flight HU7196 from Sanya to Harbin costs 19,100 yuan, which is the full price for business-class seats, with no additional markup found.

According to China's regulations on civil aviation, the pricing of the economy-class tickets is subject to control of the civil aviation authorities, while the pricing for business-class or first-class tickets can be fixed based on market demand.

To assist stranded passengers reach home, the Hainan Airlines has provided an extra 300 seats on flights leaving the island on Thursday by deploying larger airplanes, reported thepaper.cn.

The airlines has added four wide-body airplanes at its airport in Haikou and two at its airport in Sanya. It pledged to arrange more flights and seats to help stranded passengers in the following days.

According to Xinhua News Agency, as of 12 am on Friday, more than 10,000 vehicles remained in line for ferry transportation at three major ports in Haikou.

Hainan, a popular destination for Chinese tourists during the Lunar New Year holiday, received more than 5 million tourists and more than 90,000 vehicles during the week, statistics from the provincial tourism development commission show.