ESTA Since January, 2009 passengers are obligated to apply ESTA (Electronic System for Travel Authorization) for an electronic travel permission. The application must be finalized by no later than 70 hours prior to your departure and can also be submitted by third parties. If you are not planning to stay in the US but only land there for a transit, you have to specify “In Transit” and the destination in your application.
TSA The TSA-Security Program (Transport Security Administration) has been active since November 2016. It requires every airline company to forward the Security Flight Data (name in the passport, date of birth, gender) to TSA no later than 72 hours before the check-in. The goal is to prevent terrorist attacks and assure safety in air transfer. Please note that a late application can result into charged cancellations and you may also be not accepted to the aircraft. For further information please visit the following page: https://www.tsa.gov/travel/security-screening