We took ours at 6 weeks as grandparents couldn’t come to us on a 1 hr flight no problems apart feeling a right prat at the airport have to taste 4 bottles of expressed milk. There much easier at a young age tehan they are old from about 9mths to 2 years is probably the hardest age to fly with them.
Also like others have mentioned take a bottle / dummy for take off and landing as the swallowing helps them adjust to the pressure levels
Don’t hesitate. We took our daughter to Mallorca at 3 months and it was all pretty straight forward. She filled her nappy just as we were about to board so it was a bit of a rush to her changed and settled before take off.