The British Airways flight BA286 was forced to make an emergency landing in Vancouver after a medical emergency was declared during the journey from San Fransisco to London.
A total of 25 passengers were taken to hospital for smoke inhalation, according to reports in Canada.
A spokesman for British Airways said: "We are sorry for the delay to our customers' flight but the safety and wellbeing of our customers and crew is always our top priority.
This happened on the same day Heathrow Airport was given an the go-ahead for a third runway.
"The flight from San Francisco diverted to Vancouver after members of the cabin crew became unwell.
"Our ground team at Vancouver has arranged hotel accommodation for the customers and will book them on alternative flights as soon as possible."
Earlier today plans for a third runway at Heathrow Airport were backed by government.