User blog comment:Gcheung28/Fannotate the Latest Avengers: Age of Ultron Trailer/@comment-4651179-20141023230551

We can see parts of the Hulkbuster Armor flying towards Tony as the suit is assembling. That would mean Tony replicated the "Autonomic Prehensile Propulsion" part of the MK XLII in other armors.

Also, Tony can be seen wearing the XLIII underneath the Hulkbuster, could this mean the Hulkbuster will be pretty much like the original Hulkbuster and be an add-on?