The pilot of the Thomson flight from Las Palmas, in Gran Canaria, to Bristol was forced to descend from an altitude of 30,000ft to 10,000ft after the windscreen was damaged.
See also: Plane struggles to land at UK airport
Passengers were being held at Porto Airport, where '200 plus' people were made to queue for food vouchers while they waited for another flight, one passenger told the Bristol Post.
"Our plane from Gran Canaria has made an emergency landing in Portugal," said the passenger, Laura, who did not give her surname.
The windscreen was badly damaged
"The cockpit windscreen was cracked so had to descend from 30,000ft to 10,000 before making an emergency landing.
"We've been here about two hours now. Everyone is OK but a bit fed up as we are not really being told very much about what is going on other than being shunted from one part of the airport to the other."
She added: "Nobody we've spoken to knows what is going on and that includes the airport staff."
It is the second Thomson flight between Bristol and Las Palmas to make an emergency landing this bank holiday weekend.
The plane was bound for Bristol Airport
Pilots were forced to carry out an emergency landing at Manchester Airport on Saturday shortly after flight TOM6606 departed from Bristol.
Laura said passengers were only told about a 'technical fault' during her flight, before they learned after landing that the windscreen had been damaged.
She said: "There were some very nervous looking people but on the whole most people stayed calm. We had realised something was wrong before they announced it due to the sudden descent mid-flight. There was a big clap on landing."
"It was the flight stewards that told us to look at the windscreen when we disembarked," she added.
The Thomson flight was en route from Gran Canaria
Laura said at 8.20pm that they had been given the food vouchers, but 'that seems like a distant dream as there are no food places in sight yet'.
"Everyone is remarkably upbeat considering," she said.
Laura said she understands another flight has been arranged for later in the evening, but passengers were still waiting for further details at about 8.30pm.
A tweet from Thomson to Laura said: "We are sorry for the circumstances and hope you can continue your flight home soon."