Mark Sage has traveled to and from Belgium for 17 years, buying antiques for his Atlanta wholesale business.

As in other European cities, the threat of terrorism lingers in the minds of many in Brussels, he said. But he doesn't think it's forced them to significantly alter their day-to-day lives, and he doubts Tuesday's deadly terrorist attacks will either.

“I have never sensed that people are nervous or frightful,” said Sage, 51, who plans a return business trip to Brussels in early May.

Though his enterprise is comparatively small, Sage is among many metro Atlantans with business ties to Belgium.

About two dozen Georgia companies, including UPS and Delta Air Lines, have operations in Belgium, according to the Metro Atlanta Chamber. And more than four dozen Belgian-owned companies – from brewing giant Anheuser-Busch to polymer company Solvay — employ about 3,700 people in facilities in Georgia, according to the state Department of Economic Development.

Brussels is a headquarters of the European Union and the North Atlantic Treaty Organization (NATO). As such, Brussels and its metro area of about 2 million is a major hub for multinational corporations.

Atlanta and Brussels have been official sister cities since 1983, and Atlanta is home to a Belgian consulate and two regional trade representatives from the kingdom. Belgium ranked as the No. 14 destination for Georgia exports in 2015, according to U.S. Census data.

“We are deeply saddened by the tragic loss of ‎life today in Brussels,” Atlanta Mayor Kasim Reed said in a statement. “Our thoughts and prayers are with the victims, their families and loved ones. We stand in solidarity with our sister city of Brussels and the people of Belgium as they endure these unspeakable acts of terrorism.”

Many Georgia companies are closely watching the developing situation in Brussels.

Delta said Tuesday one flight from Atlanta to Brussels landed safely there on Tuesday and a second flight from New York to the Belgian capital was re-routed to Amsterdam. Hartsfield-Jackson International Airport said it remains on high alert and recommended travelers check with their airlines for the latest travel information.

Shipping giant UPS, based in Sandy Springs, said service was suspended Tuesday in some parts of Brussels, but that all its employees were safe and accounted for.

“Our thoughts are with those impacted by the tragedy in Belgium today, and we are grateful that the safety of UPS employees has been verified,” the company said.

UPS doesn’t fly regularly to Brussels, but uses the airport as a backup in case of poor weather, a spokesman said.

Atlanta-based Coca-Cola said it also will closely monitor the situation “to ensure the safety of our associates and partners, in line with ongoing guidance from the government and national security council in Belgium.”

Terrorism can make people and businesses more hesitant, said Jeff Humphreys, director of UGA’s Selig Center for Economic Growth. Fear of terror prompts government to impose new regulations and security apparatus. Companies, too, spend money on people and machines to make themselves safer.

The impact on a global economy is modest, but it is not trivial, he said, calling it “sand in the gears of the economy.”

Regulation and safety checks slow things down and reduce productivity, he said, a headwind that can drag on for decades.

“We all feel the impact on our personal productivity,” he said. “We stand in line longer. We have to do more proof of identity. It is just one more thing. We get some of it back because of technology, but we could have done that anyway.”

Spending on security may be necessary, especially if its staves off more attacks, but for the overall economy the effect is negative, Humphreys said.

Expect a temporary dip in international travel — something that will affect Atlanta more than most places, said William Pate, president and CEO of the Atlanta Convention & Visitors Bureau. “After you have something like this, especially when it involves an airport, there’s almost always a short-term effect.”

For a convention hub like Atlanta, there is a second level impact, Pate said.

“Most of our conventions now typically have 30 to 35 percent of their attendees coming from outside the United States,” Pate said.

Sage, the Atlanta wholesaler, said he has lived in Brussels, Antwerp and Ghent and he hasn’t thought twice about returning this spring.

“I love the city, I love the people and I’ll continue to go there,” he said. “You just grit your teeth and business goes on as usual.”