Passengers aboard the Islander felt a strong downdraft and saw military personnel this week as three Royal Navy helicopters conducted an exercise overhead.
Express received reports from readers that military helicopters were seen hovering over the ferry as it crossed the English Channel from Portsmouth to Guernsey on Tuesday evening.
Brittany Ferries has since confirmed that it was part of a routine training exercise with the Royal Navy, which took place between 21:30 and 22:30.
Three helicopters were involved, including a AgustaWestland AW159 Wildcat, a Merlin Mk2 and a Chinook
They are all based at Yeovilton.
A Brittany Ferries spokesperson said there were no delays to services and the exercise is run every three to four months to train Navy crews.