CLEVELAND -- United Flight 93 was hijacked in the skies over Cleveland, and for a half-hour, local air traffic controllers tried desperately to communicate with the doomed aircraft.

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Hear Tapes Of Flight 93

For two months, tape of that communication has been silenced -- until now.

ABC News obtained a copy and shared it with NewsChannel5 Chief Investigator Duane Pohlman.

For the first time, Americans will hear the voice of a hijacker onboard Flight 93 while it was in Cleveland's airspace heading back to the East Coast.

At 9:32 a.m. Sept. 11, a bloody hijacking unfolded 35,000 feet above Cleveland. United Flight 93 then made a u-turn just west of downtown.

Air traffic controllers at Cleveland Center in Oberlin, Ohio, tried desperately to make contact with the plane.

"United 93, if you hear Cleveland Center, (identify yourself) please," the tape said.

Other pilots confirmed that they heard screams.

"United 1523, did you hear your company? Did you hear some interference on the frequency here a couple minutes ago, screaming?" the controllers asked another plane.

"Yes, I did, and we couldn't tell what it was either," a pilot responded.

Then, for the first time, the tape revealed the voices of the hijackers.

"Please sit down, keep remaining sitting, we have a bomb on board," the tape said.

ABC's chief investigative correspondent Brian Ross obtained the tape of the conversations between Cleveland and United Flight 93. He will air his exclusive report 10 p.m. Thursday on "Primetime Live."

"When you heard the tape for the first time, what was your reaction to this?" Pohlman asked Ross.

"Well, it's chilling, it's wrenching," Ross said. "I don't know what else to say."

After listening to the tape, Ross said that the air traffic controllers at Cleveland Center are heroes.

"They are absolutely as cool and calm as they could be," he said. "It's hard to imagine they maintained their cool at Cleveland Center, but they did."

Air traffic controllers in Cleveland were scrambling to get other aircraft out of the way as Flight 93 changed direction and altitude.

There is nothing on the tape at the time passengers reportedly took over the cockpit, NewsChannel5 reported.