Just a few things I've noticed over the last week or so.....
Flying Club personal details online
If you log onto your FC account online, in 'Manage My Account' if you click 'update my personal details here' there's a new API section there for saving you passport number and expiry date etc. On clicking the 'Submit' button you might get an error message but you should find the details have been saved anyway.
Virgin Holiday bookings
According the their web site
here if you have a VH USA booking that includes accomodation, they will send the accom. deatils to VS for you to update your API, and I quote from the VH web site:
If you have booked accommodation with us as part of your holiday booking, then you do not need to contact Virgin Atlantic in advance of your flight, as we will provide them with this information. However if you have booked a flydrive holiday without accommodation or have booked your accommodation independently, then you will need to provide Virgin Atlantic with this information yourself at check in.
So in theory if you update your FC details to include your passport info and you have a VH booking including accom. your API data should get entered automatically before you get to the airport.
Regards