Most airlines allow only one cat per person, a few allow two in the same kennel, but they are exceptions to the rule.
“collar with ID, Rabies vaccine tag, harness, leash, vaccination record, cozy blanket and toy, portable food/water bowl, and a rolled up litter bag with litter that can be MacGyvered into a single-use litter box.”
“ Requirements for Cats Arriving in the United States
Cats don’t need rabies vaccinations to enter the United States. However, most states and many other countries require them for cats. Be sure to check your destination’s requirements and ask your veterinarian before traveling. ” CDC
Some “natural” products, such as apple cider vinegar 1), and aloe vera with abscorbic and citric acid (citation needed). Essential oils can be toxic to cats, so check ingredients on any store bought insect repellent.
Picaridin, applied to humans, does not seem to be toxic to cats, but long term research has not been conducted, and other ingrediens in the repellent need to be checked. NPIC fact sheet
Permethrin is very toxic to cats, but may be used by applying to clothing and letting dry in an area away from felines. However, permethrin would not be recommended if your cat sucks or chews on your clothing.
Some flea topicals for cats, such as Revolution, will also kill mosquitoes.