Australia's airlines have announced they are going to be stricter about carry-on luggage — in particular, how much it weighs.

The weight limit for carry-on is usually 5 to 7 kilograms, but an aviation safety expert from the University of New South Wales, Professor Ann Williamson, told RN Drive many passengers are carrying a lot more luggage into plane cabins than ever before.

"Passengers are becoming rather more generous, we could say, with the amount of carry-on luggage that they do bring with them," she said.

The extra kilos could pose a safety risk to both passengers and airline crew, and Ms Williamson suspects this is one of the main reasons airlines are pushing to restrict carry-on overflow.

"Airlines and cabin crew make every effort, as I think we all note, to make sure that these overhead lockers are closed properly before we take off," Professor Williamson said.

"The last thing you want is to have them open during flight, during turbulence, and have some 10-kilo or more object hitting you on the head.

"Having articles flying around the cabin is likely to be of danger to both travellers and cabin crew, but because cabin crew are doing this all day, every day, they're more likely to be vulnerable and more likely to be hit."

And it is not just emergency incidents that pose a risk to airline staff, Professor Williamson said.

Lifting heavier articles could pose an injury risk to airline staff. ( Unsplash: NRD )

Staff helping to move and handle larger, heavier bags could also become an operational health and safety issue.

"Cabin crew are actually having to physically move these heavier articles, and manual handling is an issue in many occupations," Professor Williamson said.

"The kind of lifting which is lifting above your head — certainly heavy lifting of that nature is going to be a challenge that [could] increase the likelihood of injury."

Professor Williamson said the weight concerns extend to the planes' functionality.

"Unknown amounts of weight on an aircraft isn't necessarily good for safety and efficiency in terms of the amount of fuel that's loaded on," she said.

As for the situations where items are removed from carry-on luggage and stored or worn elsewhere on the person's body, Professor Williamson said the rules are not really helping.

"It becomes really silly when we are just moving weight around the cabin, we're not actually stopping heavy articles being taken on board," she said.

Heavier bags slowing down travel time

Should we be carry-on minimalists? One aviation safety expert thinks there are convincing arguments to support the airlines' push. ( Unsplash: Arthur Edelman )

Professor Williamson said people taking too much carry-on with them is also adding to delays and causing hold-ups for other passengers.

"Everyone can understand why you'd want to cram more things into your carry-on, but the other thing is that it becomes less efficient when you actually have a delay in getting off the aircraft," she said.

"Certainly we're waiting longer to get off aircraft because people are lifting heavy articles and having to forage for the bits and pieces that they have in their overhead lockers.

"That is actually slowing down people getting off the aircraft and the turnaround time for airlines as well."