To resurrect this zombie thread as there is some news:
Both the Air Transat pilots from the July 2016 "incident" have now been cleared of all charges. Seems that back in 2016 the prison service deliberately destroyed evidence when the pilots were held briefly in jail.
The pilots' samples were placed within their property...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
Why it has taken till now for the charges to be dropped is unclear from the media reports.
BBC report