If an airline or immigration policy requires an onward ticket, is it allowed or sufficient for airline and immigration policies to purchase it at the last minute or after being refused check-in/entry?

E.g., if the airline's check-in front desk refuses a traveler because of lack of onward tickets, can the traveler buy an onward ticket on their phone and be right after accepted by the airline's check-in front desk?

I have crossposted the question at:

  • Comments are not for extended discussion; this conversation has been moved to chat. The comments on the question will be locked for a while, please go to the chatroom to discuss this question.
    – Willeke
    Mar 8, 2020 at 10:21
  • I don't understand why the question was closed as opinion-based by a couple (between 2 to 4) of individuals. It seems ok to me as the answer is yes, no, or it depends on X/X/Z. I don't see any opinion here. Or do we want to close all questions regarding immigration and airline policy as opinion-based, because from time to time employees fail to respect to their employers' policies? Mar 8, 2020 at 20:37
  • 2
    I've done this a few times. Was refused at check-in due to lack of proof of onward journey. Bought a ticket on my phone and then reattempted to check-in and succeeded. Maybe this depends on country and airline? If so the question is broad and not opinion-based.
    – JoErNanO
    Apr 8, 2020 at 6:03
  • @JoErNanO I don't know whether this depends on country and airline. That'd be a valid answer. I wish the question wasn't closed so that it could receive answers, even if the answer is it depends on X and Y, at least I'd know x and y. Aug 28, 2021 at 17:24