In support of KLM is Dead's contention that fuel surcharges are common to European FF programs and Delta is happy to copy them for European-origin itineraries, here are dummy bookings with British Airways and AF/KL FlyingBlue miles:

BA, nonstop LHR-ORD, coach, r/t

Total BA Miles Price per person Taxes, fees, charges and surcharges* per person Inclusive total
1Adult 50000 $ 0.00 $ 351.13 $ 351.13

Total 50000 BA Miles + $ 351.13

FlyingBlue, LHR-CDG-ORD, coach, r/t

Passenger :
1 Adult
Number of Miles required
Total 50 000 Miles
Taxes and surcharges required
Surcharges Taxes Passenger(s) Subtotal
0 503.57 1 503.57
Total 503.57 USD