A Ryanair flight from London to City of Derry had to turn back on Sunday night after the captain took ill.
Ryanair passengers were transferred onto another plane
The plane returned to Stansted airport and the runway was closed for about 15 minutes while the man was given medical assistance.
Passengers were transferred to another plane and the service landed in Londonderry at 2300 BST.
A Ryanair spokeswoman said the flight returned to Stansted after a crew member became ill.
"Passengers were re-accommodated on another aircraft."
However, the airline would not comment on the member of staff concerned.
Gavin Dalton, from Ardmore, near Derry, was in the front row of the aircraft when the man collapsed.
"He was very, very pale and his eyes were rolling in his head, absolutely motionless. The attendants ran up to him," he told BBC Radio Ulster.
"After a while, he did seem to come round a wee bit, but he wasn't really conscious."
Another passenger, Paul Walsh, said an announcement had been made to passengers that the captain was ill.
"We were approximately 15 minutes from Derry and the co-pilot came on and said the captain had collapsed and due to procedures we were returning to Stansted airport," he said.
"It was classified as an emergency...but it would be a normal landing and that passengers on board were not to panic.
"I do a bit of flying myself so I knew what was going on I knew what was happening, so I was not particularly concerned.
"I think Ryanair did what was in the interests of everybody on board."
He said passengers had been told that the captain had been taken off to hospital and that the captain's wife and family were also ill.
Ryanair, a budget airline, is one of the main customers of the Derry City Council-owned airfield and operates hundreds of flights there every year.