I Have A 5 Month Old Healthy Infant. I Have To Fly Inflight For At Least 14 Hours. Is There Any Draw Backs?
My baby was 6 months when we flew from LA to Sydney. I can suggest that you ask for a “bulkhead” seat. Qantas has seats with bassinets attached to the bulkhead for the baby to sleep in. Make sure you have plenty for formula or a light blanket to cover yourself for breastfeeding. And have a dummy (pacifier) with you to help ease the pressure on the baby’s ears during take off and landing. As a last resort also have some infant benedry with you in case the baby won’t sleep. Good luck!
I read a tip in a parenting magizine for this, Put dry formula premeasured into bottles, They normally have really hot water on the plane for tea, ask them for some fill half with hot water the rest with cold water when your ready for use, shake and serve
There were other ones but i cant remember them 
You may have problems with him when his ears pop. When my son was 6 months old he went on a plane. On the way there he was fine but on the way back he held his ears and screamed.(and screamed and screamed…) Maybe ask a doctor for advice on this.
Infants are easier on airplanes than children, just insure you have a pacifier for ascent and descent to help them with the pressure changes. (The swallowing helps adjust the pressure in the inner ear with outside air pressure.) If you have questions ask the flight attendents, they are trained in these areas. Also give alot of fluids to prevent dehydration.