Cellisttoo

We did this for my daughter on a MSP to HNL to KOA itenary on two airlines. Bought tickets in July, due in August, trip in December.

A birthdate WAS required to purchase the tickets. I called the reservations line and they said to guess. I used my due date. Since I knew she was going to be a girl and knew what her name was going to be it worked out fine. I suppose if you don't know what gender, you could just pick a gender neutral name- since at new born age you don't need to carry any documentation to fly with the child.

We then upgraded our tickets to business and called to reserve the bassinet.

The only funny incident was that on one of the flights a FA came up and said that our daughter had the same birthday as her. I said, "so you were born on [her real birthdate]?" She said, "nooooo, the manifest says [due date]." "Oh," I said, "that is because we made the reservations before she was born. That was her due date." We all had a chuckle.

BTW, check out the Baby b'air. It works great you if you will be nursing on the plane.

Edit: Just noticed that you will be flying international, which means that that the travel document must match the manifest. I would suggest that you contact NW directly and ask them for specific guidance for this situation. If you child is a lap child, maybe you can go ahead and purchase your tickets, then add the lap child later, but I don't know for sure.