Often it is large items such as generators and oil rig equipment. The USA military also uses the 124s to transport large vehicles overseas.
Many of the domestic USA flights are in support of the space program transporting satellites and launchers. Each of these flights must be done on an exemption from the Department of Transportation.
C-5s are MAC birds…Military Airlift Command. If damiross is right…about space rigging or satellites etc…then it would make sense since Nasa or a private entity would be footing the bill. And it now makes sense to ME, the area where they landed. MLB…which is very close to Titusville and the surrounding areas that is rich with government contractors. Just my guess.
Not enough aircraft! The Air Force is strained to it’s limit supporting the two current operations. They are depending heavily on civilian cargo and passenger airlift to supplement the USAF fleet.
Dami is right just now VDA 4400 landed at KHSV(Home to Marshall Space Flight Center) and a nearby rocket building plant which builds Aries 2 and now Aries 5 rockets,last time one of them came into Huntsville,they had to move the rocket overnight to avoid all the traffic and tieups moving it to the airport,which is about 15 miles away from the plant.So i don’t look for him to leave until sometime tomorrow or early am.They are just too big for either C-5 or C-17 to carry anyway,now if it is very sensitive equipment,than the military will move them as C-5 and C-17s visit Huntsville often.