All passengers and crew on a Virgin Atlantic flight were put into quarantine after landing at London Gatwick due to widespread sickness on board.
They were taken to a reception centre at the West Sussex airport for medical assessments.
Around 30 people received medical treatment at the scene and three were taken to hospital for further checks.
The Airbus A330 aircraft was met by the emergency services following an eight-hour flight from Barbados, which landed at 5.25am on Wednesday.
It was a charter flight carrying 448 holidaymakers who were returning home after travelling on the cruise ship MSC Preziosa in the Caribbean.
Passenger Trevor Wilson wrote on Twitter: “The illness seems to have originated on board ship not the plane. Five members of cabin crew became sick on flight.”
He added that the sickness was “mainly a bad chesty cough, possibly chest infection”.
A Virgin Atlantic spokeswoman said: “A number of customers on board a charter flight from Barbados to London Gatwick this morning reported feeling unwell on board.
“The safety and well-being of our customers and crew is always our absolute priority, and local ambulance services attended the aircraft upon landing to provide medical assistance.
“We are working closely with London Gatwick Airport and medical teams to offer assistance to customers, and will conduct a full investigation into the circumstances.”
A South East Coast Ambulance Service spokesman said: “South East Coast Ambulance Service NHS Trust was called to attend an inbound flight at Gatwick shortly before 5am today following reports of a number of passengers and crew feeling unwell and nauseous.
“We sent ambulance crews including our Hazardous Area Response Team and a number of other specialist paramedics to the scene.
“The crews have worked together on scene to assess and treat patients, approximately 30 people, most of whom have been able to be discharged from (the) scene with advice.
“Three patients are being taken to hospital for further checks.”
A spokesman for Swiss-based cruise line MSC Cruises, which operates MSC Preziosa, said: “We are still investigating what may have caused the illness and we are currently waiting for further updates from Gatwick Airport medical services.
“What we do know is that, on MSC Preziosa, no cases of acute gastroenteritis have been reported in the past 14 days.”
A London Gatwick spokesman said: “A small number of passengers and crew on board a Virgin Atlantic flight which landed from Bridgetown, Barbados, this morning reported feeling unwell.
“In keeping with health and safety procedures, the relevant authorities were informed and an assessment was taken on board.
“Passengers have now been able to leave the aircraft and continue their onward journeys.”