Hailstorms are Consortium helicopters with a high rate of fire. They are the first consortuim air unit you can get.
Hailstorms are affected by the upgrades Death from above, Built to last and cooling systems. The former 2 upgrade attack and armour respectivly while the latter cancels overheat on their turrets to raise the ROF.
Hailstorms are effective against Lower units and units that don't attack air units. use this to your advantage whenever you are in battle.