This question already has an answer here:
I am a British citizen eligible for the Visa Waiver Program. At Christmas, I will be flying from London Heathrow to Bogota, Colombia with a connection through the US in Dallas. As I understand it, I do not need a visa for my connection flight in Dallas.
On the return flight from Bogota to London Heathrow, I also have a connecting flight in Miami. The time period will be within 90 days of my previous transit.
Can I use the VWP to re-enter the USA for my connection, or will I need to apply for a visa?