@Spooky: MFF means Mixed Fleet Flying. Which means the ability to qualify your crews on two different types and fly them in a mixed operation. Most commonly that is currently done on Airbus types, for example A320 family with A330s, but we had the approval for MFF between 737/757 and 737/767 although we never actually did that.
Interesting to read though that Boeing doesn't offer IAN on the 747 yet, but would expect it on the -800.