Between 20% and 50% discount on many popular DLC planes, helicopters, campaigns and scenery.
DLC for this game is very expensive, so many may not consider these to be great deals, but if like me you love your military flight sims, you may be interested in these.
Eg, a few of the discounts:
F/A-18C and F16C : were A$105.88 each, now A$52.94
Mig-29, F15C and SU-33 : were A$21.50 now A$10.75
I purchased the mig 29 and f15, very happy, plane models and sound are amazing.
EDIT: for those considering the cheaper planes, I just realised that there is a plane pack called flaming cliffs which includes these planes and a few more for about $35