A controversial biography of the late John F Kennedy Jnr reveals that he was pondering selling the political affairs magazine he co-founded, George, to Rupert Murdoch the day before Mr Kennedy and his wife perished when his plane crashed off Martha's Vineyard.

The book, written by Richard Blow, a former executive editor of the monthly, also tells of tumult in JFK's marriage to Carolyn Bessette, suggesting, for instance, that shortly before their accident in July 1999 he had spent a night in a Manhattan hotel after a particularly fierce argument with her.

Extracts from Mr Blow's biography, American Son, have been published in the May issue of Vanity Fair. Its publication will be considered ironic by some because, as executive editor, Mr Blow banned staff members at George from talking about JFK in the days and weeks after his death.

As part of his effort to find a buyer for the struggling magazine, Mr Kennedy apparently went to a baseball game in New York with the two sons of Rupert Murdoch, James and Lachlan. George was owned by the Hachette Filipacchi publishing company, which closed it down soon after the plane crash.

The air accident happened when JFK Jnr was piloting his own Piper Saratoga plane, even though he had an injured ankle. He and his wife were on their way to a Kennedy family wedding in Massachusetts. Mr Blow said JFK had assured him that he would take an instructor with him.

Investigators concluded that JFK became disorientated while flying the plane in a thick summer haze after sundown.