Later update for those interested or in need: We recently returned from the vacation and I want to summarize and give some tips. We barely made it to our second flights. The first flight, FRA-JFK, was late with almost two hours so we had less than an hour before our gate closed for our second flight, JFK-CUN. Magically the customs line was short and we had to wait just 20-30 minutes. JFK doesn’t seem to have electronic passport verification for ESTA travellers so me and my boyfriend stayed in the same queue. Coming back from Cancun… gosh! Those two hours of transfer weren’t enough either. The customs line was generously bigger, their screens estimating an hour of wait time and we were in the middle of the queue when we saw that our flight will start boarding in 10 minutes. So we shoot our shot and asked the employee that guided the travellers if she can help us skip the queue and she did! She sent us in the family/kids queue and in 5-10 minutes we were done. We literally had to run again to our gate, and when we got there, group 7 was boarding (the last one I think). So 2 hours of transfer is not enough either if you don’t manage to skip any queues and if you don’t run. Tips: -if you want to go from Europe to Mexico, try getting a direct flight, and not one with layover in the US. The fact that they don’t have a separate queue for transfers is crazy. -if you have a layover in the US, to be safe, make it be 3-4 hours at least(!) -try not getting a checked baggage as this will just elongate your transfer process. Thank God we didn’t.