As a general rule, it's best to allow at least two hours for international layovers. Pack smart: Avoid packing any prohibited items in your carry-on or checked baggage. Always check with local customs officials if you have any questions.
Travelers should declare all items being brought from abroad that will remain in the United States. This includes gifts and duty-free purchases. Goods purchased in a duty-free shop are not automatically free of duty upon your return to the United States.