As massive sit-ins and demonstrations at Hong Kong's airport dragged on into the fifth day, bringing the aviation hub to a standstill and stranding passengers for a second day, Asia's financial center is feeling a worse-than-expected chilling effect on its fragile economy.

Protesters staged another rally at Hong Kong International Airport on Tuesday, after Monday's mass sit-in led to the cancellation of more than 300 flights.

The airport, one of the world's busiest passenger gateways, struggled to reopen on Tuesday morning, but was forced to suspend check-ins for remaining departures in the afternoon.

As waves of protests show no signs of easing, the city's hard-pressed tourism sector sees no light at the end of the tunnel.

The Travel Industry Council of Hong Kong, which represents travel agents in the special administrative region, said as many as 12 tour groups scheduled to arrive or leave the city on Tuesday had to be canceled, affecting nearly 290 tourists.

Another 17 tour groups departing for or from Hong Kong had to be delayed, affecting more than 300 tourists.

Cathay Pacific, one of whose pilots was charged with rioting and whose airport employees were found to have intentionally disclosed details of the Hong Kong police soccer team's flight information, saw its share price plunge by more than 2.5 percent on Tuesday.

Over the past month, shares of the city's largest carrier have plummeted nearly 24 percent, tumbling to its lowest level since May 2009.

Industrial and Commercial Bank of China - the investment banking arm of China's biggest lender - downgraded its rating on Cathay Pacific's stock to "strong sell" and slapped a price target of HK$6 (US$0.76) on it - roughly 40 percent less than what it currently trades at, and at a level that was last traded at in 2001.

Zhao Dongchen - executive director and head of raw materials at ICBC International Research - warned in his latest report on Tuesday that the recent safety alert issued by the Civil Aviation Administration of China, together with the company's poor crisis management, will cause "irreversible damage" to Cathay Pacific's brand perception and public image, which are overly exposed to the city's social unrest and Sino-US trade tensions.

The report comes on the heels of a downgrade by Bank of Communications International, which last week cut Cathay Pacific's price target to HK$11.17.

In a statement released on Tuesday, Swire Pacific - the carrier's largest shareholder - voiced its unswerving support for the Hong Kong SAR government and called for the restoration of law and order in the territory.

"We resolutely support the Hong Kong SAR government, the chief executive and the police in their efforts to restore law and order in the city. We condemn all illegal activities and violent behavior, which seriously undermine the fundamental principle of 'one country, two systems' as enshrined in the Basic Law," the conglomerate said.

"All that is special about Hong Kong - its flourishing economy and the safe home it provides for our people and families - rests on a strong and respected rule of law," it added.