No, you do not need to sit upright and straight. It helps, but the nice thing about it is that it is contoured and form fitting, with a slight lip at the bottom of the back. So if you start to sink down, it still supports your lower back. And it's made of memory foam, which means that it should adjust your own shape a bit over time. These pillows are not just great for flights. You can use them on any chair where you sit for a long time. A desk chair is perfect. It is a game changer if you spend a lot of time at a computer. I would say it is not just about the comfort of the pillow itself, but about how it takes pressure off the lower back. Try one at home first, then see whether you think it would be good for a flight.
