I stayed for 89 days in the US on an ESTA until May (met my PhD advisor, then took time off to visit friends around the country). I would like to come back for a scientific conference in July to present a paper. The problem is that it will have only been two months between the two, and I am afraid I could get denied. My questions are:

  • Is this still an issue if I am only staying for two weeks in July? (the conference + visiting friends in New York). Most previous questions seem to be about coming back for 90 days again. Would it be less risky to shorten my stay?
  • What documents can I prepare to make this easier? For example a letter of invitation from the conference, proof that I still rent my flat in my hometown, etc...

For context, I am a French national and still live and work permanently in my home country.

  • 1
    Can you clarify what the situation is with your PhD? Is it/was it/will it be in the US? Is it ongoing, finished, or are you going to start soon? What’s your travel history in the US? What’s your situation outside the US (studying, working…)?
    – jcaron
    Jun 26, 2022 at 12:29
  • The PhD is in France, co-advised by an American professor, ongoing. A French company funds it. I have visited in the US for a month in 2020 and 3 months earlier this year, and lived there for two years 2017-2019. Jun 27, 2022 at 13:26
  • I hadn't noticed you're actually presenting a paper. I suppose you're not yet at the point where you're getting paid for that, right?
    – jcaron
    Jun 27, 2022 at 14:44
  • haha no unfortunately, looking forward to it if it's ever a thing Jun 28, 2022 at 15:14

1 Answer 1


It is always difficult to guess what CBP officers will do, however:

  • The objective is for them to prevent people from actually living in the US, and more importantly from working in the US, without the appropriate visa

  • Contrary to the Schengen Area which has a very explicit rule (the 90/180 rule), the rule in the US (and similarly in the UK and a number of other countries) is a lot more informal, and subject to the appreciation of the officer.

  • Back-to-back visits up to the limit (90 days on a ESTA) are clearly a red flag, but shorter visits, or spaced visits are much less of an issue. The usual rule of thumb is to stay out as long as you've stayed, but it's by far not a hard and fast rule.

  • Since you actually have an activity in France (ongoing PhD), a valid reason to come to the US (a conference), if you do indeed plan to stay only for the duration of the conference (plus a couple days before and/or after), it's very unlikely you'll have any problems.

  • Don't try to extend the stay too much beyond that, though in my very humble opinion up to 2 or 3 weeks should be OK, but the longer you're staying, the more questions this can raise.

  • Make sure you have a confirmed return ticket.

  • Make sure you have your registration for the conference, itinerary, hotel bookings.

  • As you are presenting at the conference, anything that shows you're not getting paid for it (you're actually probably paying to do so!) could be useful.

  • Thank you ! I'll have the conference/itinerary/hotel bookings handy then. Should I accept the answer? (or maybe accept the answer if they actually let me through ? :P) Jun 30, 2022 at 15:14

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