First off, I have connected with a few engineers and pilots — I may be wrong on one point here: Commercial airplanes typically ascend/climb faster than they descend for a landing. My apologies. I’m clearly no pilot…
That being said, you can help support your baby or child’s potential ear discomfort during flying by having them suck on something like a pacifier, having them breast feed, or offer a bottle during take-off and landing. The motion of their jaw and mouth during sucking and swallowing will help them equalize to the pressure changes. When they move their jaw to suck and swallow this helps facilitate venting in the Eustachian tube that allows your child to equalize pressure from the outside world with the middle part of their ear. That click or pop you feel when you yawn is your ear drum moving back to middle after getting pushed one direction in your ear from a pressure change.
It’s true that discomfort is far greater during pressure changes when there is fluid in our middle ear (from colds to ear infections). Check in with your child’s doctor or nurse practitioner prior to flying if you’re concerned about a potential infection. If that’s not ideal, consider getting Cellscope (an iPhone app that helps you look into your child’s ear, and/or allows you to send the image to their doctor) if you’re a frequent flier and your child is prone to fluid in the middle ear.
Here’s tips for parents about fluid in the middle ear and nice summary about ears & pressure changes from Kid’s Health.