Some things you can take in your checked luggage but not in your carry-ons.
Bottles of wine, aerosol insecticides, corkscrews with blades, hiking poles, bows and arrows and pretty much any other piece of sporting equipment to which the words "stick, pole, bat or club" apply.
There are also country-by-country variations to take into account.
If you happen to be flying in the USA, you might not be allowed to board with pointy metal knitting needles.
However, they're perfectly okay in the hold, along with your personal pepper spray, a cattle prod, a sword or a Glock G19 9mm pistol provided you're compliant with Transport Security Administration guidelines, which require weapons "must be unloaded, placed in a locked, hard-sided container and declared to your airline". Do that and you're locked and loaded.
Cheeses, ditto, allowed in checked luggage but they might be confiscated from carry-on since they pong up the cabin.
I still grow misty eyed at the thought of a substantial quantity of brie and washed rind cheese from Burgundy confiscated by French security as I was about to board a flight to London.
Permitted in carry-ons
Some things you can take as carry-ons but not in your checked luggage.
The lithium batteries common to smartphones, cameras and laptops, for example – they're a fire hazard, and there is no way to fight a fire in the hold.
Smart bags with built-in power banks that can be used to power up your devices are also excluded, although if it's a cabin-compliant bag you're home and hosed.
Electric skateboards and hoverboards are also cabin-only items since they're powered by big lithium batteries, although some airlines apply an absolute ban.
A few years back Russell Crowe had a famous hissy fit at a Virgin Australia check-in desk when the airline told him his kids' hoverboards were a no-fly item.
Same goes for cordless curling irons, since they use butane, another fire hazard which can be fought in the cabin but not in the hold.
If you happen to be travelling in the USA, an emotional support animal is okay in the cabin, although airlines have called time on pooping pigs and emotional support peacocks.
An e-cigarette or vaping device is also allowed in your carry-on but not in checked luggage.
Snow globes are subject to the same strictures as any other liquid and must contain less than 100 millilitres.
Pack snow globes in your carry-on. Photo: Alamy
Ashes of your loved one – beware. Check with your airline, and since you'll probably want to transport the remains in your carry-on, they need to be in a plastic or some other container that can generate an image on the scanner.
If the ashes are in a metal container that can't be scanned it might not be allowed, and security screening staff are not going to open an urn.
CO2 cartridges are generally not allowed. If you're a cyclist and toting your two-wheeler friend along for a ride, you'll need to carry a pump for those tyres, or buy CO2 cartridges when you arrive. That's a curious one since every life jacket on board the aircraft is inflated by a CO2 canister.
Chlorine, bleach and fertilisers, no way. The ammonium nitrate in some fertilisers can be used to make explosive devices. Chlorine, like bleach, is a disabling chemical. Bear spray is forbidden for the same reason.
Rent your bear spray instead. Photo: Alamy
Meals Ready to Eat (MREs), the field rations that are distributed to US military personnel in combat zones, have a self-heating element and some airlines allow them as a carry-on item, some say absolutely not.
Possibly the weirdest item that's banned from aircraft is the humble coconut. Coconut meat, which has a high oil content, is a potential fire hazard, forbidden either as hand luggage or in checked-in luggage. It's actually copra, dried coconut meat, that's the problem, but the ban applies to coconuts generally, apart from retail packaged coconut products which are permitted.
In India, where flyers sometimes carry coconuts, either as food or as a sacred item, security screening staff will sometimes require a coconut be broken apart before it can be carried onboard.
This does not take account of the fact that it is the copra itself that is the hazard, not the liquid inside. So far there has never been an incidence of fire on an aircraft resulting from a flaming coconut, but better safe than sorry.