I suspect your legs are longer and your feet bigger than mine 
In my case it’s a backpack placed under the seat in front of mine, but I’m short-legged and in the US I buy my shoes from the children’s section. My 8yo niece’s feet are already bigger than mine :eek:
My mom and uncle’s trip was to Uganda and Tanzania. They’re both seasoned travelers themselves, having hit all seven continents and five continents multiple times each, but their previous trips had all been through tour companies like Vantage or Overseas Adventures, which handle all of the details in the background. This trip, though, was with one of our church’s priests who’s from Uganda, with them paying for his ticket in exchange for him acting as their tour guide. They were recommended the third-party company by (I think) Expedia, and since they didn’t have experience getting their own, thought that it was a good idea.
In the end, it probably wouldn’t have been too hard, if it weren’t for the stupid extra hoops the company made them jump through. But they didn’t know that in advance.
A friend of mine ran into this very scenario, some years back, when visiting Brazil. She didn’t know she needed a visa, the airline didn’t check, so she arrived in Brazil and was denied entry. The airline had to fly her back (to Miami, I think, which was not her home town). She was able to arrange the visa through a consulate there, and flew back to Brazil the next day.
Backpack tip: take it off your back and carry it in your hand in lineups and while getting on and off the plane. If you bump into me with it, I will tear it open with my teeth and eat your passport, then defecate on the shredded wreckage of said backpack.