HMS Queen Elizabeth has set sail from Portsmouth to head to the US in place of its sister ship.
The carrier is standing in for HMS Prince of Wales, which broke down off the Isle of Wight at the end of August.
The warship had been on its way to the coast of North America for three months training, including flight trials with F-35B Lightning stealth fighter jets.
HMS Queen Elizabeth's crew were notified earlier this month that they would be sailing to the US instead.
Families of crew members and well-wishers lined the walls of Portsmouth Harbour on Wednesday morning and waved union flags to see the carrier off.
The Navy has not detailed which of HMS Prince of Wales' diplomatic engagements and military exercises will be carried out by HMS Queen Elizabeth.
The programme included the Atlantic Future Forum and port stops in New York, Canada, and the Caribbean.
HMS Prince of Wales went back to Portsmouth Naval Base on Saturday after a coupling on its starboard propeller shaft broke.
The £3bn aircraft carrier will need to undergo repairs, which could be carried out at Rosyth in Scotland.
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