There is no limit to any amount of cash or monetary instruments you can bring on international flights, but any quantity above $10,000 must be declared. However, it’s not essential to declare money when flying domestically. To avoid any issues with U.S. Customs and Border Protection (CBP), travelers must be aware of the specific legal requirements when carrying large amounts of money. It is especially essential when traveling with friends or loved ones because the cash disclosure regulations may apply cumulatively.