Associated Press WriterThe nation reeled in horror as the work day began with a series of bombs and crashes that left the World Trade Center in flames and smoke billowing from the Pentagon.
"We're like everyone else, in shock," said Carol Windham, a spokeswoman at Birmingham International Airport in Alabama. Planes were grounded nationwide.
Heightened security went into effect at government and corporate offices nationwide, from the Army's main germ warfare defense laboratory in Frederick, Md., to city offices in Colorado.
"I don't think there's any place in America right now that's not at risk," said Andrew Hudson, a city spokesman in Denver, where emergency preparedness officials gathered in the basement of City Hall.
In Philadelphia, dozens of people gathered in a hotel lounge to watch television coverage.
A visitor from Texas wept.
"I can't believe what I'm seeing. I never thought I would see anything like this in my lifetime," said 20-year-old Beverly Evans of Dallas. "How can we stop something like this from happening?"