I've been on two airplane trips (one to the Republic of Panama, the other to NYC) since starting T. None of my stuff was held up or questioned, by either security or customs. I've had needles + T in my carry-on and in checked luggage. The only time something was mentioned was when TSA wanted to physically check the contents in my carry-on (it wasn't because of the needles, but because of an electronic souvenir I bought... guess it looked suspicious). The TSA worker must've seen the needles in the scan, though, because she asked if they were capped before she opened the bag. But... yeah, no problems. I even keep a letter from my doctor with my supplies stating that everything is medically necessary, but I've never needed to pull it out. Just keep the needles capped or in a sharps container, so nobody's accidentally poked if they need to examine your bag.