Everyone asks: Why is carry-on luggage never restricted?

One of the greatest frustrations of airline travel is boarding an aircraft and marching down the aisle behind someone toting a wheeled case and a substantial backpack plus whatever they’ve just purchased from the duty-free store, waiting as they heft them into the overhead bin and then finding there is no space for your own modest and weight-compliant carry-on.

Typically, economy-class passengers are allowed one carry-on bag weighing a maximum of 7-10 kgs, with the sum of the length, height and width no greater than 115cm.

Budget airlines are more inclined to enforce the rules but throughout most of the world, carry-ons are rarely and only arbitrarily checked, and it’s getting worse.

Passengers who find that airlines tolerate violations of their own carry-on restrictions are likely to bend the rules a little further next time they travel.

The reason that airlines don’t deal with this problem is the baggage beast is out of the bottle, and it’s too hard to stuff it back in again.

If an airline suddenly enforced its own carry-on limits, chaos would follow at the check-in desk. The terminal floor would be littered with people repacking their already bulging check-in luggage and then possibly finding themselves hit with excess baggage charges.

The delays would create havoc, and check-in staff would face a tsunami of passenger rage. Families with infants and small children are almost guaranteed to be travelling with excess carry-ons.

Picture a mother dealing with an infant and a toddler, luggage scattered across seats as she struggles to repack her cases? One image on Instagram, the airline would be branded "Heartless Air", and its public relations department would be in damage control overdrive.

So where does it end, this monster spawned by airlines' wilful blindness? Only when they finally play the game by their own rules, for the good of all rather than just the bin hogs. It might take the rising cost of injuries to flight crew caused by hoisting overweight carry-ons, or compensation for injuries to passengers resulting from overweight luggage falling from overhead bins, for that to happen. Or feedback from the frustrated and fuming but largely silent majority who obey the rules.