Bdtyktl

If I've got a flight booked to a country that requires an e-visa for entry (say Brazil, for example), and my visa hasn't been processed yet, but will most likely be processed within 24 hours of my flight's arrival, is it safe to board my flight, and then just wait in the transit area of the airport until my visa is approved? Or could I get in trouble for even arriving at the airport without a visa?

Would it be helpful to buy a cheap onward ticket for the next day, just in case I get asked any questions about why I'm waiting around in the airport?

Note: I'm making a few assumptions like 1) the airline doesn't check if I have a visa and I'm able to board the flight 2) the visa will be approved 3) I am flying with only carry-on bags 4) I already have an international SIM in my phone 5) if the visa isn't approved for any reason, I could just buy an onward flight to somewhere else.

You won't get in trouble for arriving at the airport without a visa. Instead, the airline you're flying won't let you on the plane to depart in the first place. They can check the status of electronic visas at the time you check in. They do this because the airline is responsible for transporting you back out of the country if you are refused entry. If you don't have a valid visa, and you need one, you will be refused.

Judging from my personal experience (primarily with JFK and MIA), your tickets will be checked by the airport staff/security regardless of whether or not you're going to clear the customs or proceed to the transit area. If there are no transit passengers on board, there may not even be an option to get there as the corresponding door would be locked.

While this is impossible to say whether or not you would be "lucky" with the visa check upon departure and the ticket check upon arrival, generally such a strategy sounds like a risky undertaking.