Aircraft carrier HMS Prince of Wales may miss important flight trials with F-35B Lightning jets off the US coast after it suffered a propeller shaft malfunction shortly after setting sail, the Royal Navy has confirmed.
The £3 billion warship left Portsmouth Naval Base on Saturday before an "emerging mechanical issue" occurred off the south-east coast of the Isle of Wight.
Forces News understands that the carrier is in sheltered waters allowing specialists and divers to inspect the starboard shaft.
It is understood once these investigations are complete, the team will be able to understand where the repair can be conducted and whether temporary engineering solutions are required.
The departure of the NATO flagship had already been delayed from Friday because of a technical problem, although it is not known if the incidents were related.
Shortly after the 65,000-tonne ship sailed on Saturday, a mechanical fault was discovered with the starboard shaft.
The carrier languished about five miles from Shanklin before it moved back to Stokes Bay at Gosport, Hampshire, travelling at a rate of four knots accompanied by tugs for the return journey to calmer waters.
The waters of the Solent and Stokes Bay, in particular, are much calmer than the English Channel.
Rear Admiral Steve Moorhouse, director of Force Generation, who is responsible for making sure Royal Navy ships are ready to deploy, said in a video statement: "I've been to the ship today to see for myself what the issue is and how we in the Royal Navy can work together to make sure the ship can successfully return to her tasking.
"After the initial assessment, it's likely that the fault will require repairs which may impact the ship's programme.
"The ship is now moving to a more sheltered anchorage for further inspection and then we'll be able to provide further comment on the nature of the issue and the impact to her current schedule."
He added: "We've reacted quickly to the emergent defect and are working closely with industry partners to resolve this as soon as we can.
"Rest assured, the Royal Navy continues to meet its commitments to deliver operations and to keep the UK, our partners and allies safe."
Specialist website Navy Lookout said a photograph of the carrier leaving Portsmouth shows a wake only on the port side, suggesting a problem with the other propeller shaft.
It added that unless the problem can be resolved at sea the warship might need to go into dry dock at Rosyth, Scotland, months ahead of a planned inspection in 2023.
The £3 billion carrier had a colourful send-off as it departed on Saturday afternoon and passed thousands of music-lovers at the Victorious music festival on Southsea Common in Portsmouth.
Pop act Sugababes were in the middle of their set when the giant ship sailed past with the crew lining the flight deck to get a view of the festival.
The NATO flagship is sailing to undertake training exercises with the US Navy as well as the Royal Canadian Navy and United States Marine Corps.
The programme is expected to include exercises with the F-35B Lightning jets.
Watch: HMS Prince of Wales leaving Portsmouth last week for drone and fighter jet drills.
A Royal Navy spokesman said on Saturday: "HMS Prince of Wales will cross the Atlantic with her task group, ready to push the boundaries of uncrewed technology and the tactics used by the UK’s two new Queen Elizabeth-class carriers.
"Along with notable port stops in New York, Halifax in Canada and the Caribbean, the next three months will see the Prince of Wales task group work closely with US allies, operating F-35B jets and uncrewed systems which will define Royal Navy aviation of the future.
"With fleet flagship HMS Queen Elizabeth also set to deploy to the Mediterranean and Baltic this autumn at the heart of a potent Royal Navy task group, it will mean both UK aircraft carriers will be operating F-35B jets thousands of miles apart."
Watch: What is wrong with HMS Prince of Wales?