A kirpan is a ceremonial knife that serves as part of the traditional daily garb of Sikhs around the world. In the United States, according to the Transportation Security Administration (TSA), knives of any kind with blades that are longer than 2.5 inches and that are fixed, are not allowed to be carried on a flight.
: https://www.learnreligions.com/are-kirpans-ok-when-flying-3969877