A Portuguese airline has apologised for keeping more than 100 passengers stranded at Stuttgart airport after one of its flights was cancelled at the last-minute because of a drunken co-pilot.

Shortly before the TAP Air Portugal flight was due to take off to Lisbon on Friday night, an airport employee noticed the co-pilot walking unsteadily and smelling of alcohol.

He notified airport authorities, who decided to keep the plane on the ground. It was not immediately clear if the 40-year-old co-pilot was detained.

The German news agency dpa reported that all 106 passengers were put up at hotels overnight.

TAP tweeted that the passengers would only be able to fly to Lisbon on Monday, “which is, at the moment, the first day with seats available”.