THIRTEEN hours in the air, eight toilets, and 26 passengers violently ill with gastroenteritis.

It was the trip from hell for those on a Qantas flight from Santiago, Chile, which touched down in Sydney yesterday.

The sick passengers, believed to be from one party, were suffering before they embarked on the flight.

A Qantas spokesman said. "It was a tour group that had food poisoning so it was contained to them."

Sixteen members of the group were taken to Prince of Wales and St George hospitals including three who left the airport on stretchers, a NSW Ambulance spokesman said.

Scores of family members were left high and dry in the arrivals hall with no official word from Qantas over the incident. Passengers were held up by the gastro-stricken group who had been traveling to Brazil for the Pope's World Youth Day visit.

David Sanhueza and his family from Mount Druitt were left waiting two hours for his mother-in-law, Carmen Caro, visiting from Chile.

"They don't give you any information, there's nothing out of the speaker. I went and saw customer service but they wouldn't give me anything," he said.

Her granddaughter Jennifer Sanhueza said the family only found out from the news.

"We weren't told much, we only heard from a phone call that it was all over the news," she said.

Mrs Caro said the group that got on in Brazil had been vomiting the whole flight.

"A whole lot of kids got on the plane at Brazil and they were all vomiting and sick," she said in Spanish, translated by her granddaughter.

Bernie Herrenberg was left waiting, balloons in hand, for the return of his 23-year-old daughter Stefanie.

"I've been waiting and all I know is what my daughter texted me," he said.

A statement from the NSW Ministry of Health said the group had developed "vomiting and diarrhoea on the plane" consistent with norovirus infection, a common cause of gastroenteritis. The flight was aboard a Boeing 747-400, which has a total of seven toilets located on the main deck and one on the upper deck.

As a precaution, other passengers have been advised to keep a close eye on their health over the next 24 to 48 hours and seek medical advice if they become unwell.