Pack enough food, enough toys and provide the opportunity for them to rest on the plane in your carry-on luggage.
A stern word and a few consequences almost always work. Take them into the bathroom for time out if you need to. That should silence anyone!
Talk to your child before, during and after the flight, so they know exactly what to expect. If they know what’s coming, they are less likely to be upset about it.
The worst thing you can do is delay flying with a toddler because you are frightened of it. It will only be worse when it is time to take the plunge as they won’t know what to do.
If your child is feeling anxious or fearful of flying, give them a toy or a teddy to distract them from that fear.