Chickens' ears are not as sensitive as human ears, so they do not need protection from the engine noise of a plane. In fact, chickens are fairly resilient when it comes to noise - they will get used to normal sounds around them and it won't bother them in the same way it might bother a human. However, it's still important to make sure the chickens are comfortable during transport. The most important thing is to make sure they are properly secured during the flight to prevent injury. You may also want to consider covering the carrier with a light sheet or towel to help keep them calm during the flight. Overall, while chicken ear muffs might be a cute idea, they are not necessary for their comfort during a flight.