Futures are in the red

US stock futures were trading in the red on Tuesday morning ahead of the start of the session.

Near 7:15 a.m. ET, Dow futures were off 30 points, S&P 500 futures were down 5 points, and Nasdaq futures were down 12 points.

Top of mind around the world this morning are the two explosions in Brussels. At least 28 people were killed in the attacks on an airport and metro station. Public transport is under lockdown. No clear motive has been established.

European stock indexes were also trading a bit lower, with the Euro Stoxx 50 off 0.2%.

Shares of airlines that operate in the region were also under pressure. Ryanair, an Irish low-cost airline, fell as much as 2% in Dublin. Lufthansa was down 1.5% in Frankfurt trading. Air France fell 4.5% in Paris.

In an email to clients, Marc Chandler and his currency strategy team at Brown Brothers Harriman noted that the attacks are dampening sentiment across the market.

They wrote, "The attacks come as Europe prepares what for many will be a long holiday weekend. Gold, the dollar and yen seem to have been the beneficiaries. Bonds are generally firmer and equities lower. However, in late morning activity in London, the markets began stabilizing."

Gold gained about 0.6%, or $8 an ounce, to as high as $1,260.80. The 10-year yield fell one basis point to 1.905%.

In US economic data today, we'll get the preliminary Markit manufacturing PMI for March. After a number of solid regional readings in the past few days, economists will be looking out for whether there is truly a turnaround in the sector.

The FHFA house price index for January is also due.

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