Julie, it's good to be thinking in advance about making your daughter comfortable for her plane ride. Some children don't experience any problems with their ears on flights, and some do. It's usually only a problem during takeoff and landing, when the air pressure in the cabin is changing.
Our ears naturally adjust to changes in air pressure through our Eustachian tubes, which connect the middle ear, behind the ear drum, to the back of the nose/throat. During takeoff and landing you might feel pressure and popping in your ears, and you might yawn, chew gum or swallow to help your Eustachian tubes open up so your ears will adjust to the pressure. Babies, however, have narrower Eustachian tubes and sometimes they don't open up as easily to equalize the pressure. This can cause pain for the baby and lead to fussiness and crying.
A good way to help prevent ear pain is to have your baby drink from a bottle or cup during takeoff and landing. (If your baby is strapped into her car seat in her own airplane seat for take-off and landing, which is safest, you won't be able to breastfeed.) Your baby is more likely to experience ear pain if she has nasal congestion from a cold or allergies, which can cause swelling of the Eustachian tubes. If that's the case ask the pediatrician whether you should give your baby an antihistamine/decongestant for the flight. Be sure to use the dosage the doctor recommends.
In addition to watching out for your baby's ears, it's good to prepare for other possible challenges in caring for your baby during the flight. Make sure you have enough snacks and drinks for your baby; diaper supplies; and entertainment and comfort items such as books, music, stuffed animals, toys and a favorite blanket. When babies get bored on flights, parents often have to walk them up and down the aisle. Some parents find it easier to fly at night so their baby can sleep through the flight.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.