Two pilots accused of planning to fly a plane from Scotland to Canada while under the influence of alcohol have been cleared after key evidence was destroyed by prison staff.

Jean-Francois Perreault and Imran Zafar Syed were arrested in 2016, minutes before a flight from Glasgow to Toronto was due to take off.

Blood tests were said to have found them above the legal alcohol limit.

But the case collapsed when prison staff destroyed some of the samples.

The Canadian pair were due to fly an Air Transat plane with 250 passengers on board when they were arrested at Glasgow Airport on July 18, 2016.

They were taken to Helen Street Police Station in Glasgow, where they were interviewed and blood samples were taken.

The charge stated Captain Perreault had 32 milligrams of alcohol in 100ml of blood, while first officer Syed had 49 milligrams in 100ml of blood. The blood alcohol limit for flying is 20 milligrams.

They were also accused of acting in a threatening manner and fighting at the Hilton Hotel in the city on the same day.

At the police station, each blood sample was split in two - one of each for the prosecution and one for each pilot.

The pilots' samples were placed within their property, as they were in custody, and remained there during their initial court appearance, during which they were remanded in custody.

When the pilots arrived at Low Moss Prison in East Dunbartonshire, prison guard Paul Scoular said he thought the samples would be worthless evidentially and, along with the prison nurse, destroyed them.

A Crown Office spokesman said: "It is the duty of the Crown to keep cases under review.

"After full and careful consideration of the facts and circumstances, including the recent decision of the Court of Appeal, Crown Counsel instructed there should be no further proceedings at this time.

"We are working with Police Scotland to ensure there are proper processes and guidance in place covering the retention and storage of samples when an accused person is remanded in custody."

Mr Perreault, of Ontario, and Mr Syed, of Toronto, had denied all the charges against them.

Both pilots had been suspended by their employer Air Transat following their arrest.

They are now due to fly again after being cleared of all wrongdoing.

An Air Transat spokesman said: "We will be meeting with them in the next few days to plan their reinstatement since there is no charge against them and we have no evidence that they have broken any law, nor our internal rules

"They will need to undergo retraining and requalification as per applicable legislation, and we will put in place measures to ensure that their behaviour is exemplary."