A China Southern Airlines plane took off from Shenzhen International Airport bound for Amsterdam, the Netherlands, on Monday as the airline resumed the overseas route after a long hiatus.

Tickets for the flight have become hot items, with return tickets for Monday set to sell out, according to a statement released by China Southern Airlines on Tuesday.

With the Chinese Lunar New Year approaching, there is a strong demand for international air tickets as China has optimized its COVID-19 policies and the Civil Aviation Administration of China will relax restrictions on international flights starting on Sunday, authorities said.

In a notice, the CAAC said China will no longer define high-risk inbound flights and will cancel their 75 percent seat occupancy limit.

The round-trip between Shenzhen and Amsterdam will operate twice a week — on Mondays and Wednesdays — according to the statement from China Southern. The aircraft is an Airbus A330, it said.

It marked the opening of the first direct passenger route linking Shenzhen with the Netherlands, which is also the first new international passenger route opened by the airport in the past three years, signaling a potential recovery in the international passenger transport business once decimated by the COVID-19 pandemic.

It's expected to help build an air bridge between Shenzhen and Amsterdam, an aviation hub in Europe, playing a role to enhance economic and trade cooperation and cultural and personnel exchanges between the Guangdong-Hong Kong-Macao Greater Bay Area and the European Union, said Shang Huili, route manager with China Southern Shenzhen branch.

As of the end of December, the airline had resumed international routes from Shenzhen to Jakarta, Moscow, Dubai and Singapore.

China Southern's Shenzhen branch said it is planning to gradually restart routes to the Philippines, Vietnam, Cambodia, Thailand and major cities around the world this year.

Pan Qingzhong, a professor from Tsinghua University, said domestic and foreign airlines are now operating only 840 international passenger flights every week in China, compared with 18,230 before COVID-19.

He made the remarks at a forum recently hosted by the Academic Center for Chinese Economic Practice and Thinking, which is part of Tsinghua University.