The use of military air traffic controllers for civilian traffic is not unusual, but has been deprecated in most developed countries. In the US, the Federal Aviation Administration (FAA) operates a wholly parallel system with that of the US Air Force and NORAD. This is also the case of Eurocontrol and each of its member nations' air defense systems. Brazil's use of an integrated command poses some unique challenges to the government. As members of the military, controllers are not allowed to form unions (such as the case of NATCA in the US) or to strike.