An EasyJet flight was reportedly diverted to enable police to arrest three men suspected of taking drugs in the toilet.
A steward found a bag with a substance, thought to be cocaine, in the toilet three hours after take-off.
The trio were seen making repeated trips there and later became abusive to crew.
The pilot told the 181 passengers on the Manchester-Tenerife flight they would land in the Portuguese capital of Lisbon.
He added: “Police are about to board. Do not get out of your seats.”
Ten police took the men and their luggage off the aircraft.
Lisbon police said the British trio appeared in court.
A spokesman told The Sun: “They were arrested on suspicion of illegal activities on a flight.
“They were found with an envelope with traces of a suspected illicit substance. Tests have so far proved inconclusive.
“They were released pending the decision of the judge, who is still investigating and will hear from witnesses, including the crew.”
EasyJet is thought to have banned the men for life.
The airline said: “The flight was met by police due to three passengers behaving in a disruptive manner.
“We don’t tolerate abusive or threatening behaviour.”