* Explosions in Brussels kill at least 26 people
* Airline stocks hit hardest
* Gold jumps about 1 pct
* Futures down: Dow 42 pts, S&P 7 pts, Nasdaq 18 pts (Adds details, comment, updates prices)
By Abhiram Nandakumar and Tanya Agrawal
March 22 (Reuters) - U.S. stock index futures were lower on Tuesday after explosions in Brussels sparked fresh geopolitical concerns and sent investors scurrying for safe-haven assets.
Two explosions tore through Brussels airport on Tuesday morning, in what Belgian public broadcaster VRT called a suicide attack, and another blast struck a metro station in the capital shortly afterwards. At least 26 people died in the attack.
European markets fell, while traditional safe havens gold and government bonds firmed up as reports of the events in the de facto capital of the European Union unfolded. Airline and travel-related stocks were the worst hit.
Shares of American Airlines, Southwest Airlines , Delta Airlines and United Continental Holdings were down between 3.4 percent and 1.1 percent in premarket trading.
Delta and United Airlines rerouted flights to other locations following the attacks.
Gold rose 1 percent to $1,255 an ounce, while oil prices were swept lower by investor nervousness.
"It's a market that's on the edge right now, but we're not seeing investors panicking," said Peter Cardillo, chief market economist at First Standard Financial in New York.
S&P 500 e-minis were down 7 points, or 0.34 percent, with 205,633 contracts traded at 7:42 a.m. ET (1142 GMT). Nasdaq 100 e-minis were down 18 points, or 0.41 percent, on volume of 26,057 contracts. Dow e-minis were down 42 points, or 0.24 percent, with 31,562 contracts changing hands.
Cruise operator Carnival Corp's shares were down 3.6 percent at $48, while travel-website operator Expedia was off 2.5 percent at $108.08 and peer Priceline fell 1 percent to $1336.60.
For financial markets, the events in Brussels come at a time when liquidity is starting to dry up ahead of the Easter holiday and investors are planning to cash in on a steep rally in stocks over the last few weeks.
The S&P 500 has risen about 8 percent in the past five weeks and is about 4 percent away from its all-time high.
"We're getting to the point in time where we're overbought in the short run. I wouldn't be surprised heading to the long weekend if we saw some profit taking," said Art Hogan, chief market strategist at Wunderlich Securities in New York.
The Brussels attacks eclipsed encouraging economic data out of the euro zone, while Asian shares had faltered earlier over hints from U.S. Federal Reserve policymakers about an earlier-than-expected increase in interest rates. (Reporting by Abhiram Nandakumar and Tanya Agrawal in Bengaluru,; Editing by Don Sebastian)