You can fly with any amount of cash, without any legal restrictions. The TSA (Transportation Security Administration) has no rules limiting the amount of money you can bring through security. However, if the TSA suspects that the money is related to any type of criminal activity, such as drug trafficking or money laundering, it can refer the matter to an airport law enforcement agency. In this case, the money could be confiscated and you may have to go to court to have it returned.
Most experts recommend carrying only a small amount of emergency cash when traveling. However, if you're flying to a destination where American ATMs and credit cards don't work, you may have no choice but to carry large amounts of cash. In this case, it's best to keep the money in your hand luggage and secure it with a TSA-approved padlock. Never leave it out of your direct line of sight.
If you are chosen for a secondary (additional) check, tell TSA agents that your suitcase contains cash and that you should keep it in sight during the check. In addition to any controls, keep your money in a safe place out of sight. If you want to carry the cash in a banknote belt, you can put it in the airport bathroom after going through security. Once again, there is no legal limit on the amount of cash you can carry through a TSA checkpoint.
Customs and Border Protection may ask you to justify any unusual amount of money you have with you, and your answers (or lack of them) and your general behavior could result in law enforcement entities confiscating your money. So if you're carrying a large amount of money, make sure you have a legal and legitimate reason to do so, and take some extra time at the airport in case you have to explain why you're carrying it.
