Voices From the Sky

"United 93" hits the multiplex this week, with harrowing dramatizations of what took place on board the hijacked plane on Sept. 11, 2001.

But some key facts about the flight's hijacking are left out of the movie entirely. An audiotape obtained exclusively by ABC News provides one of the clearest and most accurate records of the United 93 hijackers.

Click here to see the video.

Radio transmissions between United 93 and an air traffic controller in Ohio include sounds of blood-curdling screams. The hijackers themselves take the microphone, speaking over the open airwaves, as they pilot the plane toward what would be its final destination, the Pennsylvania earth.

For veteran air traffic controller John Werth, the morning started like any other: he reported for work at the Cleveland Air Route Traffic Control Center in Oberlin Ohio, which handles high-altitude planes as they pass over the country.

News of the tragedy in New York was just starting to spread when Werth heard something unusual over his headset: muffled screams and a voice yelling, "Get out of here! Get out of here!"

Amid a flurry of rapid transmissions from other pilots in his crowded airspace, Werth desperately tried to figure out what was happening.

At 9:32 a.m., the answer became clear. The hijackers now had control of the cockpit and made an out-of-breath announcement, likely intended for passengers, that was instead transmitted on the Federal Aviation Administration frequency.

"Ladies and Gentlemen here. It's the captain, please sit down. Keep remaining sitting. We have a bomb aboard."

Minutes later, another ominous transmission, likely hijacker Ziad Jarrah: "Hi, this is the captain. We'd like you all to remain seated. There is a bomb aboard. And we are going to turn back to the airport. And they have our demands so please remain quiet."

Over the next half hour, Werth calmly and repeatedly tried to contact United 93, some 20 times, in vain. All the while he rerouted other planes flying nearby, even asking nearby pilots for their help as "eyes in the sky," to spot the hijacked plane once it disappeared from his radar scope.

But in the end, all he could do -- all any air traffic controller could do -- was watch.

Werth, along with other controllers in Cleveland, Boston, New York and Washington, was later honored for his work as a first responders on Sept. 11.

But Werth does not want to be called a hero. He was not at the movie's premiere in New York this week. He did not walk the red carpet, or attend the fancy party after the movie was shown.

Retired and living in Ohio, he prefers to stoically maintain that all he did on Sept. 11 was his job.