I flew my grandson and his parents to their home 4 weeks after his birth on a trans-Atlantic flight. Non event. Secure in his carrier seat, which was strapped to the cabin seat. Never cried out or anything. He has flown a couple of times since (now almost age 2). Again visiting Grandpa
One thing to keep in mind during climb and descent when traveling with infants, let them use pacifiers. Chewing on the pacifier will apparently dissipate the pressure differential.
But I really understand other passengers frustration when young children cry out in the cabin.