There are many reasons why babies cry on planes, but the most common reason is the cabin pressure pressing down on their delicate ears. Babies' ears are more sensitive than adults' ears, and they are generally not able to equalize their ears as adults can. During a flight, noise levels inside a plane can reach a level that can damage your baby's hearing, so it is always a good idea for them to wear ear muffs when they fly. Unlike adults, babies aren't capable of intentionally "popping" their ears - however, we can help them by encouraging them to swallow. You can do this by offering your baby a pacifier or bottle.