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.
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.