Two words my friend: Combined Arms
A tank may be a sitting duck against helicopters and low performance aircraft on it’s own, but it has several offensive measures it can employ when the aircraft goes to nap of earth (NOE) to avoid SAMs. These surface to air missles are almost always organic to the motorized unit or mechanized unit.
Offense:
http://www.globalsecurity.org/milita...d/m2-50cal.htm http://www.globalsecurity.org/milita...tions/m943.htm http://www.globalsecurity.org/milita...ons/m830a1.htm
Defense:
http://www.defense-update.com/products/a/arena-e.htm