I haven't done 16 hours but I did take two little DDs half way across the US and on to Dublin, and have also taken two of the others to Dublin from the US midwest with stopovers in JFK and Heathrow at age 1 and 4.
Enlist the help of some nice woman near you just to keep an eye on the baby when you go to the loo, and ask the staff for help whenever you need it. Take advantage of time when the baby sleeps to go to the loo. Don't wait til you're about to explode.
Get a bassinet the airline provides or book a second seat and bring the baby's carseat along with you for sleeping. Try to relax and sleep when the baby sleeps.
Ask the staff to hold onto your meal until the baby is sleeping if that's possible. Eating is very difficult when the baby is awake.
Ask the staff for help with bottles, etc. If the baby is used to a warm bottle, now is the time to gradually introduce cooler formula, not when you're in midair and no-one can help you warm a bottle. If you're breastfeeding, keep drinking.
It's easy to get dehydrated when you fly. Drink more than you think you need.
Bring more nappies than you think you could possibly need. Ask the staff for a secluded spot for nappy changes and to dispose of soiled ones.
Don't go nuts trying to entertain the baby. Keep it low key and follow the baby's rhythms. Let the baby play peep with passengers in the seat behind but don't wear them out. Bring little toys that don't make too much irritating noise, and board books. Let the baby rip magazines. Walk up and down occasionally for a change of scenery and to stretch your legs.
Try not to get tense if the baby cries. Ignore the rude tutting of other passengers if you encounter a rude few. Resist the urge to slap them.
Crying will sound much louder to you than it will to anyone else, in reality.
Make sure your carry on bags are streamlined. Don't carry anything extra beyond your passport and ID and some money, plus toiletries for yourself in your handbag. Bring a bulging baby bag on board and do not put it in the overhead bin. Keep it where you can easily reach it.