In movies and the such the military has a craptastic record against zombies.. Nevermind that dead bodies will add to the zombie horde (do we factor in civilians into this?) and taking heads off won't help (white walker on headless horse) only fire can stop them.. But years of television and movies tells real earth military something different so they are all aiming for the head and avoiding fire so not to have flaming corpses latching onto them. Sure they can figure it out eventually but how quickly when you factor in all the other threats on the table? Wizards/Death Eaters, trolls, archers (elf accuracy), Orc horde, ghost army, human soldiers (cannon fodder but will take up precious ammo), Demontors, giant birds, walking trees, Nazgul/Ring Wraiths, balrog, Dragons (not sure if the hobbits dragon and mountain giants are applicable here)
Any initial air strike won't wipe the enemy out and the fantasy enemies have ways of countering it once it's recognized as a threat. (Wizardry, Demontors, nazguls on fellbeasts, flying balrog and crap like that)
I do but airstrike would be the first response anyway. I can see orcs being catapulted for no reason and crushing people. The ammo required to take down some of these threats would be high as not everyone in the military are elite marksmen in the heat of battle. (Or at all)
Area 51 can't count for much since we don't know what's behind those doors.. Could hold unstoppable weapons, failed experiments, Alien corpses, super soldiers, another threat to the military to add to the table or nothing.
Wrote this quick so forgive any out of sort bits.