The Transportation Security Administration (TSA) is primarily focused on aviation security and looking for prohibited items like weapons, explosives, and flammable materials; they do not specifically look for money. There is no legal limit on how much cash you can carry on a domestic flight within the United States. However, if a TSA officer discovers a very large amount of cash during a routine search, they are permitted to notify law enforcement (like the DEA or local police) if they suspect the money is linked to criminal activity, such as drug trafficking or money laundering. For international flights, the rules are stricter: you must declare any amount of currency or "monetary instruments" totaling $10,000 or more on a FinCEN 105 form. Failure to declare this amount can result in the seizure of the money and potential legal penalties.