Chicago (CNN) - Mitt Romney marked the 11th anniversary of the September 11 attacks Tuesday by greeting firefighters and first responders gathered on an airport tarmac in Chicago.
It was an impromptu stop for the presidential candidate, who thanked the emergency personnel stationed at the airport and observed the anniversary on the tarmac.
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The line of first responders marked the moment the first plane hit the World Trade Center by saluting for a moment of silence, a large American flag draped over their trucks.
Romney's motorcade arrived 15 minutes later, after the flag had been taken down.
When he arrived at his campaign charter at Chicago's O'Hare Airport, the Republican presidential candidate climbed out of his motorcade, put on a blazer and walked over to the line of emergency vehicles.
Romney then shook hands with the line of men in firefighter uniforms who stood in front of four yellow fire trucks with flashing lights, and thanked them for their service.