A passenger stricken with acute pancreatitis on a United Continental Holdings Inc. flight to Rome sued the airline over the crew's refusal to land the plane so he could obtain treatment.

Lewis Christman and his wife Roseanne filed a complaint against the airline alleging he suffered such severe pain and nausea during the May 2016 flight from Chicago that he was unable to sit up, and lay curled up on the galley floor in a fetal position. Upon landing, Christman was hospitalized, first in Rome and then in the US for months, and later required surgery, according to the complaint filed May 17 in Cook County, Illinois state court.

"When there is an emergency situation with someone who was as sick as Mr. Christman was, United Airlines has an obligation to land the plane, and get him to the emergency room as quickly as possible," said David Axelrod, a lawyer for the plaintiffs.

The allegations are another blow to the Chicago-based airline after a string of public-relations disasters, including the death of a dog stored in an overhead bin and last year's violent dragging of a passenger off an over-booked flight. The decision whether to divert a flight for a medical emergency isn't an easy call for airlines, which risk incurring vast costs and complaints from other passengers.

"We are aware of the suit and are looking into the matter," said Erin Benson Scharra, a spokeswoman for United.

Christman claims that the flight crew was ill-prepared for the emergency, initially failing to offer him assistance, couldn't find pain medication and declined a recommendation from a doctor on board that they divert the flight. The crew also failed to contact a ground-based medical team about Christman's condition, which worsened as a result of the delay in treatment, he says.

He says he was given a business class seat, where he spent the remainder of the flight in agony. The couple, who are alleging negligence and loss of consortium, are seeking at least US$100,000 in damages.

Christman, who lives with his wife in McHenry County, Illinois, said he was told that his pancreatitis had become necrotic, or seriously infected, by the time he landed. He said he was given basic medical attention, transferred to a public hospital and then moved to another hospital in Rome, where he remained for several days.

Advised by doctors that he was too ill to fly on a commercial airline, he returned to Chicago on a chartered Air Ambulance with his wife in June 2016. He stayed at a hospital there for three months. Complications from his condition required surgical removal of his gallbladder and gastric bypass surgery, according to the complaint.