Having been on a Jet2 flight to Ibiza recently there is a dichotomy in the airline’s management of these issues.
While they have prominent policies to try to reduce problems, and don’t sell alcohol until 0800, they actively promote the sale and consumption of alcohol. The flight had a flight time of 2:50. Take off was at 0710 and from 0800 there was 3 alcoholic drinks services. There were announcements encouraging passengers to buy extra alcohol to consume on their onward transfers to the resorts. There was a 4th unofficial sale of alcohol to a drunken group as the trolley came back to the front of the plane. Luckily the group of boys involved just managed to keep to right side of exuberant, but it was on a knife edge. I would not have liked to see their reactions during an emergency exit.
Overall Jet2 is a well run airline and their staff are always professional and courteous. The problem is that of company policy.
Considering the options for airport drinking prior to boarding, 4 drinks services is irresponsible and not in keeping with the publicly expressed policies. The airlines do need to take some blame for drunk passengers too!