Every year airport officials confiscate tonnes of butter.

Photo: 123RF

Despite restrictions being in place for a decade, the Aviation Security Service (Avsec) group manager of operations Karen Irwin said people still have not got the message about carrying gels on international flights.

"I think everybody understands the restrictions around liquids. So if you're fronting up to a security check in and you have a bottle of water, it's going to get taken off you. But what a lot of people forget about is the aerosols and gels part of it. A gel is anything you can smear, and that's going to get taken off you," she said.

"So that precious mānuka honey you've bought, put it in your check in bag. If you're taking Marmite for your loved ones overseas, put it in your check-in.

"The other one that is astonishing and we confiscate tonnes of it every year, is butter. Because there is obviously a lot of ex-pats living overseas desperately wanting some good old New Zealand butter and their family lovingly take it in their hand luggage and it gets taken off them."

She said sadly the confiscated items ended up in landfill, although they were working on a scheme to donate the unopened goods to the likes of the City Mission.

Because the restrictions only apply on international and not domestic flights, she said a lot of people only encounter it once a year when they fly off for their summer holiday and most people do not necessarily go overseas every year.

"We know that from the time people throw their things in their suitcase and walk out the door, their brain has switched off and people are almost on auto pilot."

New Zealand does not have liquid, aerosol and gel restrictions on its domestic flights, but a lot of other countries do, including the United States and the United Kingdom.

She said people need to be aware of their duty free. If you buy duty free, arrive at another country and then connect with a domestic flight, you may need to slip that into your checked in luggage.

"So if you are getting liquids make sure they're in tamper proof bags that the duty free people will give you. Don't take them out of there and it's a good idea to save a few kilos of space in your bag and you can slot it into your domestic bag."

She said as a general rule of thumb a litre of water weighs about a kilogram.

Ms Irwin said the lack of restrictions on domestic flights meant a lot of people only encounter it once a year when they fly off for a summer holiday and a lot of people do not fly overseas every year.

If in doubt, check the website but the simple rule is; if you can smear it, you should pack it.