It's not speculation really. Currently, the FAA allows infants from 1 week old to fly and here's a press article showing how babies travelled on aircraft in the 1950's:
https://www.boredpanda.com/vintage-infants-airplane-skycot-boac-flights/
If the rules have changed, then there should be a record of it that you can find to support your assertion.
It’s not up to me to prove that Stanley Ann would have been allowed to take a <1 mo old baby on a 2,683 mile flight. I have said all along that if SA had had the baby in HI she’d have stayed there. I also maintain that her parents got her out of HI long before airline rules could have been an issue. This explains why no one has confirmed they saw her in HI from the end of the fall ‘60 semester until she returned in ‘63, why no one has any earthly idea where in HI she (supposedly) lived, why no one remembers her going to the hospital or coming home, why an address was used on the BC at which SA was NOT living, etc. etc.
If my entire theory hinged on SA being allowed to make such a marathon flight with a newborn, then it would be up to me to prove that airlines in ‘61 allowed newborns in such circumstances. Your reference/link is not to a newborn. Nor do you address the fact that technology was nothing in ‘61 compared to what it is today. Personally, I absolutely do not believe such a tiny infant would have been allowed on a 2,83 mile flight back then. But I don’t have to prove that bc all known facts point to Stanley Ann already being in the Seattle/Vancouver area when the baby was born.
Btw, what is your theory as to why SA would have rushed out of HI under the circumstances? Had she given birth there, she had many reasons to remain. Why would she have undertaken such an upheaval in her life?