I was on such a flight several years ago. Mom would NOT correct the child at all. A grandmother in the row in front of me mentioned to the mom that the child might be in pain from the change in air pressure. She then offered a Benadryl so that the child would not have to be in pain.
Worked like a charm. Mom thought she was helping her child, child so was asleep. The rest of us didn’t have to listen to the screaming brat.
I once offered a Benadryl to a mother on a flight and you would have thought I’d offered her poison for her child. ‘I WILL NOT MEDICATE MY CHILD UNNECESSARILY’. I said, ‘your child would be happier’. I was glared at for the rest of the coast to coast flight.
Some children have a paradoxical reaction to Benadryl; they get hyper instead of sedated. Which is a good reason to do a trial before a flight.
I would be very hesitant to offer a parent medication for a child. What if there were an unknown allergy or adverse reaction?
Smart Grandma.
Years back...I worked overseas and traveled back to the US once per year with my family. My son HATED flying and was very hard to control.
Prior to yet another flight, our family doctor suggested Benadryl. It did work like a charm. Kid is happier, parents are happier, other passengers are happier.