Singapore's air show began Tuesday with the usual ribbon cutting and displays of aerial prowess, but also with less typical warnings to industry and military figures attending to avoid handshakes and other close contact to avoid spreading a virus that has sickened tens of thousands of people.

Some heeded the advice, opting to bump elbows or bow instead of gripping hands. But human habit being what it is, there was still plenty of handshaking, elbow grabbing and other glad handing as the show got underway with roaring fighter jet fly-bys and helicopter acrobatics.

Dozens of exhibitors and most Chinese participants cancelled due to travel restrictions and concerns about the new coronavirus, which has sickened dozens of people in this Southeast Asian city-state.

But authorities said the show, held once every two years, should go on even after a business meeting at a city hotel last month led to the virus spreading to several countries. Officials have urged calm while also deploying police around quarantine quarters to ensure that patients or those suspected of having the virus do not share it further.

At the event's formal opening, Deputy Prime Minister Heng Swee Keat urged those attending the air show to forego handshakes and other contact by using other greetings, such as the traditional Chinese clasping of one's own hands, bowing or just waving.

Heng acknowledged the blow to the aviation industry from the outbreak, which has caused cancellations of tens of thousands of flights, mainly to and within China but also affected regional travel. The air show has scaled back by half the number of people allowed to attend when it's opened to the public later in the week.

"Depending on how the situation changes in the coming days, additional measures may be introduced," Heng said. "Your well-being is of utmost importance."

Heng said more than 930 companies had opted to participate in the show, "suggesting the Singapore Airshow is still regarded as one of the world's leading aerospace and defence exhibitions."

While some major manufacturers of aircraft, engines, components and software decided to sit out this event, some 40,000 business visitors are expected to attend, he said.

Top military brass are out in force, highlighting the competitive market for defence-related aviation and aerospace equipment at a time when the U.S. is launching its own space force.

Singapore's air show is one of dozens held worldwide every year. But it is a highlight for the industry in a vital market and a key marketing and dealmaking opportunity for U.S. defence contractors.

The U.S. is the largest participant in the show, R. Clarke Cooper, assistant secretary of state in the Bureau of Political-Military Affairs, said in a conference call with reporters.

But the eagerness to sell is tempered by concerns over risks of theft of U.S. military technology and over risks that partners might be pulled into deals with other governments where they might compromise their own strength.

"We don't want a partner to put themselves in a position where an introduction of, say, significant Chinese or Russian platforms or systems put at risk, either their credit, their finances, or even put at risk their own tech -- not just ours but their own technology and their own military capabilities," Cooper said.

Anchored by China's 1.4 billion people, air travel in the Asia-Pacific region is growing faster than the global average, at 5.4% a year, according to a global market forecast by Airbus.

That is further fueling the long intense competition between market leaders like Airbus and Boeing, but also within the region as China and Japan work to build up their own indigenous aircraft industries.

Most Chinese participants have withdrawn from the show due to travel restrictions: Singapore is barring entry to any foreigners who have visited mainland China in the past 14 days and requiring local residents returning from China to undergo a period of quarantine.

Still, the Chinese People's Liberation Army Air Force aerobatics team Ba Yi will be performing, as will the U.S. Marine Corps' F-35B Joint Strike Force and the U.S. Pacific Air Forces' F-22 Raptor.

That followed Singapore's aerial display on Tuesday of an F-15SG fighter jet and AH-64D helicopters.

The 70 exhibitors that cancelled plans to attend, most after Singapore raised its health alert from yellow to orange last week, include Lockheed Martin and Raytheon Co., Bombadier, De Haviland, Gulfstream and Honeywell Aerospace.

Mitsubishi Aircraft Corp. was showing off its Spacejet, a regional aircraft that it hopes might gain certification in 2021. The Japanese aircraft maker is competing heavily with Chinese rivals that had to stay away from the Singapore show.

Mitsubishi's first delivery will be in Japan, but its initial focus will be on the U.S. market, which accounts for 40% of the global regional jet market. As eager as the company is to finally bring its jets to market, it's not rushing, said Jeff Dronen, the company's strategic communications director,

"We're putting importance on aviation safety," he said. "It's also about building an industry in Japan."

Like many at the show who travelled from other Asian countries affected by the virus outbreak, he saw little added risk from attending, given the rising number of confirmed cases of the coronavirus in Japan, he said.

Singapore has nearly 900 people in quarantine or isolation, the government said Monday. The latest two cases were a 37-year-old man who served quarantine papers on two people who were infected, and a 2-year-old girl who was evacuated from Wuhan, the city where the virus was first reported. Of the 45 people confirmed to have been infected with the virus, seven have fully recovered, the Ministry of Health reported.