Now i know a child under 16 cannot fly alone on a plane, and has to be accompanied by an adult.

This may be true for various low cost carriers, but some legacy carriers like British Airways, Air France and Swiss still allow children to fly as UMs (Unaccompanied Minors). Certain seats are allocated to children travelling in this category, usually within easy sight range of the galley and jumpseats. UMs do not have a choice of where they are sat.

I'm taking 14 kids under 16 on a plane on saturday (2 planes actually) we will all sit together, I shall insist (unless the airline bumps me up to 1st class)!