Do I need to show return tickets at the airport in the US with ESTA as a German?
I plan to fly with German citizenship from Spain to the US - San Francisco. I got already an ESTA 
I read in every source that you need an backflight for getting a ESTA. I filled out the form for the ESTA for some while ago without any return tickets. I am not sure if they wrote something like "at the airport you need return tickets to show". Do I need return tickets or is it just optional?
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Do you need a return ticket to enter US on ESTA?
It is of course obligatory to hold a return ticket to complete your ESTA application and here we will explain the reasons why. An ESTA authorisation is possible when your visit to the United States is for a period of no longer than 90 days.Do you need to show proof of ESTA at airport?
Do travelers need to bring a paper printout of their travel authorization to the airport? No. DHS will be able to communicate a traveler's ESTA status to the carriers.Do you need flight details for ESTA?
There is no requirement at this stage, to add flight numbers and accomodation information onto an ESTA, it is optional (at the moment) but you do have to input information into the airlines database which is cross referenced to your ESTA by passport number.Is ESTA required for transit in USA?
ESTA is required in all cases of entering the U.S. Travelers must apply for and receive ESTA even when transiting in the U.S. to a third country without a visa. You must apply for ESTA in any of the following cases: transit, transfer, or stopover (layover).HOW TO FIND CHEAP FLIGHTS - My Best Tips After Booking 500+ Flights
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