Some may think storm in a teacup but MA15+ films are legally restricted. Just look at the Australian Classification board guide for showing a film publicly.
When showing a film in a public place, there are age restrictions that apply for certain classifications. This section outlines the restrictions, explaining which classifications can be shown to which age groups.
www.classification.gov.au
MA 15+ restricted
MA 15+ films are legally restricted. MA 15+ films are not suitable for people under the age of 15.
People showing MA 15+ films cannot allow a person under the age of 15 into the film unless they are with a consenting parent or guardian.
The guardian must be an adult with parental control over the child. This could include a grandparent, aunt or uncle, but generally not an older sibling or friend.
The parent or guardian must stay with the child during the film.
In Queensland, the person accompanying the minor can be any adult.
The plane left Sydney. A quick look at NSW legislation shows corporations facing up to 20 penalty units per minor ($2,200). So the fine could be quite large depending on how many people aged 0 to 14 on the flight who didn't have a consenting parent. Clearly there were a few of them as they tried to disable screens like whack-a-mole until eventually terminating the broadcast.