Believe it or not, there are more witch-friendly items allowed in your carry-on than you might think. You can put together a witchy kit full of essentials and keep it in your carry-on so you're always prepared. First though, a little disclaimer. At the time of the creation of this list, all items have been checked against the TSA allowable list. As we all know, policies and regulations change over time. So, it is always a good idea to double check this list and your airline's policies to avoid having to toss something out when going through security.
To create an image of what this will and will not include, I want you to think of a make-up bag. This is about the size to aim for. This kit is just for your tools on the go. You can always bring things like a book (or five), your e-reader, and a towel to serve as an altar cloth, but they will not be included in the kit for space reasons. You also don't need to create a tool kit if you don't want. As I say in Paganism for Prisoners: Connecting to the Magic Within, all the tools you could ever need are already a part of you. But that doesn't mean that carrying a kit with some essentials won't help your mindset be geared towards magic when you travel.
Divination: I have some great news: your pendulum is fine to take on board, as are your tarot cards. But let's say that you don't want to risk damage to these tools. Well, you can improvise with a sewing needle on a string and a deck of playing cards. Sewing needles are surprisingly effective for those quick answers you need on the spot. Stick it in a little sewing needle box and voila.
Candles: As long as they are the solid type, e.g., solid wax or battery-operated tea lights, you can take these with you. I love using birthday candles because they come in many different colors and are small, so they don't take up much room. I also recommend a bar of soap or so Play-doh so you have an on-the-go candle holder.
Fire: You can bring a disposable lighter or matches with you on the plane. The conditions are that the lighter can't be the electronic type and the matches cannot be the strike-anywhere type. Keep it simple and stick with the ones you can get for a dollar at the store, and you'll likely be fine.
Earth: Color me delighted to learn that my bag of "writing stones" got to come with me on a recent trip overseas. That's right, you can bring rocks. You can also bring sand and salt. I would just caution to use a bit of common sense and not take large rocks. But that piece of Black Tourmaline, that beloved Citrine, and even that Bumblebee Jasper can all have a place in your travel kit.
Air: For the element of air, I like to bring a light essential oil like Sage, Pine, or Lemon Verbena. You can also use perfume or cologne. They just have to follow that 3.4 oz/100 mL rule. There are some lovely travel cases for oils, wooden covers, or you can put it on a cord on wear it on the plane.
Water: The simplest thing to do is carry a water bottle and fill it. Hopefully you are going to a place with running, drinkable water. If you are not, there are probably arrangements in place for drinking water.
Offering Libation: Alcohol is allowed in your carry on. No, this isn't to help you with your nerves on a bumpy flight. It is to serve as your traveling offering. The two guidelines to follow is that it needs to be under 140 proof and no larger than 3.4 oz. Juice of the same size is allowed, but here's a handy trick. Just buy a bottle of your preferred beverage once you get through security. It is a bit more expensive, although duty-free shops help offset the cost, but you get to carry more.
Offering Food: Yay for snacks! As long as they are solid you can take a lot of types of food with you. Some of my favorites for your witchy kit are crackers, dried fruit, and seeds. They will have a long shelf-life and are small enough to not take up all your room.
Athame or Wand: Nail care is important, but it is also practical because one of the easiest temporary wands or athames is a nail file, metal or glass based on your preferences. If this isn't your style, you can bless a wooden pencil, a knitting needle, or a crochet hook.
Thread/String: Depending on the type of magick you do, you may just need a spool of black, yellow, or white thread to sew protective symbols into your clothing. Or you may want a length of string or rope that is 4.5 feet long (this is a traditional method of measuring a 9" circle).
Mirror: A little compact mirror is great for scrying, reflecting moonlight, introspective magic, and for a great deal of other purposes. Mirrors are iconic in their ability to help one be transported to another world. With this in mind, having one can be helpful for trancework.
Bag: The bag, or box, you use for your supplies can be as simple or elegant as you would like it to be. I mentioned earlier that makeup bags are great, not just because of their size, but because if you pull a makeup bag out in front of people, everyone assumes what the contents are and go about their day, no questions.
You know the flavor of your magickal practice better than others. So this next part is a list of other items that might, in your mind, seem like magical necessities. For example, herbs, tea, and spices are allowed as long as they are dried. Who can't think of many uses for herbs? Also consider a scarf, bobby pins, corkscrew or bottle opener (without the knife), safety pins, seashells, small scissors (under 4"), tape, and a flashlight. If you have room, a small statue of your patron deity is also a welcome addition.
To sum up, you've got a little bag, and in it the following: A pendulum, box of birthday candles, soap or Play-Doh, disposable lighter or matches, stones, essential oil, water (that you get after security), offering food and libation, nail file, thread, mirror, and some miscellaneous items. This is all it takes to form a basic witchy, TSA-approved travel kit.