Confusion, panic and realpolitik – new tape throws light on the day JFK died

Newly released recording shows tension between Lyndon Johnson and Kennedy's mother

The release of an audiotape lost for almost five decades has provided new details of one of the grimmest, most harrowing flights in history – the one that carried a murdered president, his wife, top aides and his successor from Dallas to Washington on the afternoon of 22 November 1963.

Until now, it was assumed the only surviving recording of conversations aboard Air Force One as it flew back with John F Kennedy's body was an edited version prepared by the Johnson administration and handed over to the LJB Presidential library, which in turn made it public in the 1970s. But now the complete tape, which runs for 2 hours and 22 minutes and contains 42 minutes of new material, can be heard. It was made for JFK's top military aide, General Chester "Ted" Clifton Jr, who was aboard Air Force One that day, and who kept the spools of tape at his home.

Gen Clifton died in 1991 but after his wife died in 2009, his estate sold the tapes to the Raab Collection, historical document dealers. Raab put one copy of the tape on the market for $500,000 and gave another to the US National Archives, which this week made it available to the public. The full version is a fly-on-the-wall account of how America's leaders coped with the shattering events of that day. The circumstances are chaotic, and rendered even more so by the crackle and static of the original recordings, as emergency calls are patched though, in a blizzard of passwords and codenames.

The new material does not rewrite history. But it adds new details and some personal exchanges – as well as one tantalising piece of ammunition for conspiracy theorists.

Lyndon Johnson had been sworn in as President only minutes before Air Force One took off from Love Field in Dallas, less than two hours after JFK had been pronounced dead. In flight, he calls the mother of the slain president to express his condolences. "I wish to God there was something that I could do," Mr Johnson says, "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." Then she quickly ends the conversation – a sign perhaps that relations between her son and his vice-president were in fact often far from easy.

The murder of Kennedy posed logistical problems, unimaginable only hours before. What vehicles would collect the body at Washington's Andrews Air Force Base? Where would it be taken, and would Jackie Kennedy, her pink suit still stained with her husband's blood, accompany it?

At one point, Gerald Behn, the head of the Secret Service, can be heard discussing arrangements, suggesting a "black Cadillac", and maybe ambulances. "I would get them out there anyways, regardless," he tells an assistant.

During the flight, officials frantically seek to have calls patched through to colleagues, often referred to by codenames, to let them know what's happening. "I want november alpha bravo 90," someone asks, "I'd like to talk to Monument who's aboard that aircraft."

Most sinister – for conspiracy buffs at least – is an aide's urgent request to get in touch with his boss, General Curtis LeMay, then Chief of Staff of the US Air Force, and the ultimate Cold War hawk.

General LeMay, who was the role model for the manic General Buck Turgidson in Stanley Kubrick's Dr Strangelove, was a constant critic of JFK, whom he regarded as an appeaser. The peaceful resolution of the Cuban Missile Crisis, he once said, was "the greatest defeat in our history". No less salient for conspiracy theorists, his whereabouts on 22 November 1963 had never been known – until now. On the tapes, an aide of General LeMay tries to reach his boss. "Colonel Dorman, General LeMay's aide," he identifies himself. "General LeMay is in a C140. Last three numbers are 497, SAM C140. His code name is Grandson. And I want to talk to him."

Why was that demand made, and why was it edited out of the LBJ Library version? To protect codenames and other sensitive national security information is the most reasonable explanation. But some Americans – three-quarters of whom believe the government covered up the truth about the assassination, according to a 2009 poll – may not be so easily convinced.

On Air Force One: The excerpts

President Lyndon Johnson: "I wish to God there was something that I could do ... and I wanted to tell you that we are grieving with you."

Rose Kennedy: "Thank you very much. Thank you very much. I know you loved Jack. And he loved you."

Mrs Johnson (nicknamed Lady Bird): "Mrs Kennedy, we feel like we just had..."

Rose Kennedy: "Yes, alright."

Mrs Johnson: "We are glad the nation had your son as long as it did."

Rose Kennedy: "Yes, well thank you, Lady Bird... Goodbye."

"Kennedy apparently shot in the head... He fell face down in back seat of his car, blood was on his head. Mrs Kennedy cried 'Oh no' and tried to hold up his head" – an unidentified White House operator notifies Secretary of State Dean Rusk of the shooting. "General LeMay is in a C140... He's inbound. His codename 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" – An aide tries to contact General Curtis LeMay. The general's whereabouts at the time of the shooting had – until now – been unknown, fuelling theories about his involvement in the assassination.