There have been at least three jailing (6 months seems to be the norm) in Europe in the last little while for flying whilst intoxicated.
I certainly don't for a moment condone it. I think at a minimum it is an offense worthy of dissmisal and a lenghthy license suspention or cancellation in aggrievated circumstances.
HOWEVER, when it comes to jailing people, I look at it like this- we KNOW that drink driving costs tens of thousands of lives world wide every year. Yet the punishment for a first DUI offense is a fine and short suspention of license.
We have NO EVIDENCE of ANY fatal accident being caused by an over-the-limit airline pilot, yet it seems a given that it is an offense punishable by jail time.
It seems to me it is a law driven by perception rather than fact.