If you fly on airplanes and you are prone to falling asleep or you need to get decent sleep while flying, consider buying an inexpensive cervical collar. The pliable foam wrapped in cotton will hold your head neutral and provide a “shelf” for your chin to rest upon. I won’t promise it will send you into a deep sleep but, you will dramatically reduce the risk of sprain and strain to your cervical ligaments and muscles. If you’re interested, search “pliable foam cervical collar.”