Assuming you are asking about how to get an infant to sleep on an airplane:
There are a few things that can be done in order to make an infant more comfortable and hopefully fall asleep on an airplane. One is to bring along their favorite stuffed animal or toy from home as a way to help them feel more secure in this new environment. Another is to try and keep the same bedtime routine as much as possible before boarding the plane. This means keeping mealtimes and nap times close to when they would normally occur. Once on the plane, it may be helpful to create white noise by using a portable fan or downloading a white noise app on your phone. If your baby does happen to fall asleep, it is important not to disturb them too much so they can stay asleep for longer periods of time.