It may well vary depending on the country you’re flying from but in the UK the precise prohibition is:
Knife (with a sharp or pointed blade and/or blade longer than 6cm) | No |
That is any knife with a blade longer than 6cm OR a pointed blade of any length, including less than 6cm OR a sharp blade of any length, including less than 6cm.
... so basically no ‘functional’ knife.
some who think they’ve read the guidance see only ‘6cm’ and fail to see the ‘sharp and pointy’
That prohibits, for example the ‘box cutters’ (Stanley knives) used with tragic consequences on 9/11. Clearly the blade length is well under 6cm, but I wouldn’t want to try taking one of those through security in the US.
Think about it folks. You may well be a fine upstanding citizen, but do you want to be on a flight these days with 300+ others, any of whom were allowed to carry a Swiss Army knife on board?
We’ve been round this circle before. At the security check in UK airports there’s a bin full of knives, scissors etc which the barrack room lawyers, also present here, will tell you categorically should be allowed on board.