Offramp wrote:
Is it possible that part of the problem is air-conditioning? All car
drivers know that if the AC is on then all the windows should be shut.
Did a designer think, "There is no need to have openable windows because there will be AC"?

Perhaps, but the bus only has 'air cooling', not proper air-conditioning. I
assume the problem with fitting proper air-conditioning is that the bus is
already overweight.