U.S. stock index futures indicated a lower open on Tuesday as traders worried about explosions in Belgium, killing more than two dozen people at the airport and metro system.
Dow futures were about 50 points lower, off their worst levels of the session. The U.S. dollar index was slightly higher, with the euro near $1.1226 and the yen at 111.73 yen against the greenback as of 9:05 a.m. ET.
Shares of American Airlines and Delta Air Lines were both off more than 2 percent in pre-market trade.
In Europe, the pan European Stoxx 600 Index was down 0.6 percent, with downward moves across European markets.
"I regret to say, yes it is (logical) and the short term reaction is that investors will exit the airlines sector, the transport sector, the travel sector, the leisure sector and there will be a flight to quality in the dollar as we are seeing in the movement on the dollar-euro," Bob Parker, senior advisor at Credit Suisse, said.
In oil markets, Brent crude traded at $41.28 a barrel, down 0.63 percent, while U.S. crude was at $41.17, down 0.82 percent.
Fed speakers today include Chicago Fed President Charles Evans and Philadelphia Fed President Patrick Harker.
In U.S. economic news, domestic home prices rose 0.5 percent in January on a seasonally adjusted basis from the previous month, according to FHFA. House prices were up 6.0 percent from January 2015 to January 2016.
On the earnings front, Nike, Red Hat and Krispy Kreme are among companies due to report today.
In Asia, Japan's Nikkei closed up 1.94 percent, while the Shanghai Composite in China closed 0.60 percent lower.
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