The US National Archives has released long-lost recordings of the Air Force One flight back to Washington on the day of John F Kennedy’s assassination.
The tapes contain 42 minutes of audio that was not included in the original public version.
It includes discussion about what to do with the slain president’s body and a phone call to Rose Kennedy, his mother.
The material was donated by a rare documents dealer, who acquired it from the estate sale of a Kennedy aide.
The tapes provide new insight into the grief and confusion in the highest levels of the US government in the hours after Kennedy’s shooting in Dallas, Texas, on Friday 22 November 1963.
Kennedy adversary pinpointed
Lyndon Johnson, who had just been sworn in as president, can be heard – barely audible through the crackle – consoling the dead president’s mother.
Mr Johnson is on the plane with the body and Jackie Kennedy. She is still wearing clothes covered in her husband’s blood.
Vice-President Lyndon Johnson was sworn in soon after JFK’s assassination
“I wish to God there was something that I could do,” says Mr Johnson. “And I wanted to tell you that we are grieving with you.”
Rose Kennedy can be heard responding: “Thank you very much. Thank you very much. I know you loved Jack. And he loved you.”
There is also audio of the attempts to contact Secretary of State Dean Rusk and other cabinet members in an aircraft codenamed Wayside which had been over the Pacific en route to Asia.
“This is the [White House] Situation Room,” says an official. “Relay following to Wayside. We have report quoting that the president is dead, that he died about 35 minutes ago.”
The tapes also shed light on the previously unknown whereabouts of former Air Force Chief of Staff Curtis LeMay, an adversary of Kennedy.
In the recording, an aide can be heard trying to reach the general.
“General LeMay is in a C-140,” says the aide. “He’s inbound. His code name is Grandson. And I wanna talk to him… If you can’t work him now, it’s gonna be too late, because he’ll be on the ground in a half-hour.”
Experts say the comments are likely to stir debate among conspiracy theorists, who have long questioned why audio was missing from the official recordings in the first place.
The National Archives has made the audio available to the public for the first time.