Originally Posted by LondonMiles

I guess they have to impose this restriction otherwise everybody would credit to US and then redeem their US miles on Virgin Upper Class without paying the really high fuel surcharges.

Although the same logic applies to economy bookings and you can still book these.

Don't forget that you can credit Virgin flights to some other Star Alliance airlines such as ANA and they have mileage based redemptions so there can be some good opportunities to redeem on shorter inter-contintental flights.