Twenty years ago, we could not have asked for a more beautiful morning; one bursting with the promise of happy things. With summer waning, the sky was a brilliant blue, and barely a cloud was in sight. We had no way of knowing then the unspeakable terror the morning would bring. We had no way of knowing how this day would change our lives forever.

7:59 a.m. American Airlines Flight 11 departed from Boston Logan International Airport, heading to Los Angeles, with 92 people on board.

8:19 a.m. United Airlines Flight 175 left the same airport not long after Flight 11, also bound for Los Angeles, with 65 people on board.

8:20 a.m. American Airlines Flight 77 took off from Dulles International Airport, a third plane on its way to Los Angeles, with 64 people on board.

8:41 a.m. United Airlines Flight 93 departed Newark Liberty International Airport, bound for San Francisco, with 44 people on board.

Four huge jets began their horrific flights, carrying four to five terrorists each and enough fuel to cross the country. Still, we were blissfully unaware. Still, we were innocent to an evil beyond our imagining.

8:46 a.m. Those of us watching morning news shows or listening to the radio heard with concern that a plane had crashed into the North Tower of the World Trade Center in New York City. Every television station’s cameras were trained on the smoking skyscraper while newscasters guessed at what happened. We imagined a horrible mistake, some fault of engineering, or an accident that rendered the pilot unable to fly. Our hearts went out to those who surely perished, both in the building and on the plane.

Instantly we thought of loved ones who lived in New York City, who worked at the World Trade Center, who might be there now. We thought of friends and relatives who were first responders or those who had flights that day. Could they have been in the building when the plane hit? Could they be rushing toward the building in a fire truck? Could they have been on the plane? Surely not, we told ourselves, surely not. We picked up our phones to call only to find phone lines impenetrable. For some Columbia residents, those calls would never, ever go through.

We did not know then that this crash was no mistake, no engineering failure, no accident, but we would find out all too soon.

8:50 a.m. As a nation, we watched camera feeds switch incongruously to an elementary school classroom in Sarasota, Florida, where then-President George W. Bush was reading to a group of second graders. We watched his face turn grave and his jaw set while an aide whispered in his ear.

9:03 a.m. We listened to newscasters’ coverage of the plane crash and saw black smoke billow from the North Tower. Then, our jaws dropped in horror as an impossibly large aircraft, Flight 175, hurtled into the South Tower in an explosion of fire, glass, and black smoke. Our tears flowed as replays showed the plane fly into the building again and again, evilly dipping its wing at just the last moment, assuring maximum damage.

All other, more comprehensible theories fell away in that instant. There could be no more denying it: America was under attack.

9:37 a.m. Flight 77 plowed into the Pentagon, smashing through its thick concrete layers like a machete through tissue. We hung our heads in dismay. How many more planes are out there, we wondered? What will they hit next? How many more will die?

9:42 a.m. The Federal Aviation Admin-istration, in an unprecedented move, grounded all flights inside of or on their way to the United States.

One more hijacked plane was still in the air. Where was it?

9:59 a.m. We watched in disbelief as the South Tower fell to the ground in a mountain of steel and gray smoke. Newscasts followed gray ash-covered people as they fled Ground Zero.

10:07 a.m. We breathed a sad sigh when we learned the last hijacked plane had crashed into a lonely field outside Shanksville, Pennsylvania. It was one weaponized aircraft that thankfully did not find its target.

10:28 a.m. In a final heartbreaking moment, we watched as the North Tower followed its southern brother to the ground, collapsing into a gray, smoking pile of ash.

A piece of our collective innocence vanished forever in the space of just two and a half hours. Planes in the sky would never again be something magical. The deaths of nearly 3,000 innocent souls cleaved a hole in our hearts that still bleeds today, 20 years after Sept. 11, 2001.