Im looking for some help understanding how I can use the new formation out of the Agents of the Imperium book. I must be misunderstanding something here, and I hope a veteran can help me out.

This is taken directly from the official GW FAQ page:

Q: Can units that are Battle Brothers embark in each other’s Transport vehicles during deployment?
A: No.
Q: Can units from two Detachments with the same Faction embark in each other’s Transport vehicles during deployment? A: Yes.

In the Agents of the Imperium book it states on page 35 that each units faction is shown as a symbol. In this case the faction is "Aeronautica Imperialis". So, being that the Forces of the Aeronautica Imperialis are their own faction, what could I possibly choose to embark on a valkyrie other than the formations optional officer of the fleet? Am I missing something here, because I would like to embark a unit of astra militarum veterans , but as i understand it, they are a different faction (Astra Militarum) and cannot be embarked during deployment. The valkyrie is not a dedicated transport, and is essentially its own faction and flyers always start in reserve so...