Looks like Airbus's attempt to smoke through the extended range fuselage center aux tank design has been stopped by the FAA. The traditional extra baggage bay tanks won't work because they would use up too much room, so Airbus designed a new center section tank that goes right to the fuselage skin on the center belly in order to be big enough to hold the required fuel.
Airbus tried to skate over the obvious issue of what would protect the tank in the event of a belly landing and got EASA to approve it anyway. Now looks like FAA will require major structural changes to provide tank protection. I think the MAX fiasco has forced the FAA to start being more authoritative when asking skill testing questions and this new unwillingness to just rubber stamp the manufacturer's data will become standard for all regulators
It will be interesting to see what EASA does about the MAX dash 7 ands10 certifcation.....