Simple answer
Add £5 to the ticket price.
All the £5s are collected into a pot (so £500 or so in the pot).
There are three questions to answer about the safety briefing.
All the answers get put into a hat.
First three correct entries drawn win part of the pot (£300, £200, £100).
OR
Cabin crew are legally permitted to punch non-observers in the face.
Seriously people, it's sub-5 mins (not all aircraft are the same, equipment does get changed).
Oh, and one more thing: after landing, sit down until the light goes off. Can we legalise breaking people's legs too?