curious You cannot fly Finland to Australia without a stop-over, simply because no commercial plane can cover the distance.
Typical routes from Europe to Australia have at least one stop-over either in an Arab country (i. e. Dubai if you fly Emirates) or in Asia (e. g. Singapore).
then it would be good to know how many hours it is. for peeing i can also imagine the solutions @Abby82 offered, but in the end @Maija has to negotiate with the family.
Abby82 Actually could you just carry the belt in luggage and lock it on after the security check ?
this could also work, it is not forbidden to wear the belt on the plane and if it is put on after the security check, it should work. the question is whether the belt is not too big for the hand luggage.
Maija
you definitely don't need thighbands in an aeroplane. Abby is right, just put the belt on after the security check and you're good to go. π