An acceptable way of sorting List
I needed to find the largest amount of passengers


If you need just the largest amount, you don't need to sort the whole list (which is slow*), you can instead walk though the list, remember the largest amount found so far and update that as you iterate the list.

LINQ already contains a method that does just that, called Max().



* Sorting is \$\mathcal{O}(n \log n)\$ with a good algorithm, or \$\mathcal{O}(n^2)\$ with a trivial algorithm like the one you used; finding maximum is just \$\mathcal{O}(n)\$.