I wonder if Stanley Ann’s mom was pushing for Barack Sr to honor his fatherhood and make everything legal with a marriage. She may have pushed for the in-person visitation of her daughter in hopes that she could have charmed Onyango into allowing his son to marry her. The plane fare may have come from Stanley Ann’s mom with the idea that things would work out in the end with the dowry going to the wife’s parents. There is also the idea that this would provide Onyango to make a new Muslim conversion, which is something he did as a young man.
Baby Obama was described as a large baby, which may have helped in getting through the restriction for newborns on planes.
Further evidence would move the theory up a bit on my credibility ladder, but at the moment i'm still leaning towards a birth in Canada. Far simpler and more understandable explanation. Far cheaper as well.
I'm not going to hold this theory if evidence argues against it though.