Flying Blue is the frequent flyer programme of Air France - meaning that all flights coded as AF are treated exceptionally in Flying Blue.
Therefore, AF-coded flights always earn in Flying Blue*, regardless of who operates the flight (even non-Skyteam or non-FB partner airlines, such as FlyBE as you mentioned above).
In other Skyteam programmes, such non-Skyteam operated AF-coded flights WOULD NOT EARN.
The same applies for all KL-coded flights (and presumably also for all other flights bearing the code of an airline that has FB as their native programme - namely UX/Air Europa, SB/Aircalin, RO/Tarom, KQ/Kenya Airways).
When you buy a DL-coded flight, however, you are no longer dealing with a flight coded AF- or KL- (or another native FB airline). Therefore, the usual Skyteam requirement that the flight be both coded by, and operated by, a Skyteam or Flying Blue partner kicks in.
VS is NOT a Skyteam airline and neither is it a Flying Blue partner.
Therefore, DL???? operated by VS won't earn in Flying Blue.
Neither would VS???? operated by DL earn in Flying Blue.
You can claim mileage for these flights in either Delta or Virgin Atlantic's programmes if you wish.
*subject to normal AF earning rules. Though I am pretty sure that non-earning MiNi fares are not offered on such "partner operated" flights.
Last edited by irishguy28; Jul 28, 2015 at 8:01 am