 Pilots of revenue flights periodically must demonstrate PAR approach proficiency, and GCA controllers must conduct a minimum number of such approaches in a year to maintain competency.Because of their labor-intensive nature—one GCA controller is normally required for each aircraft on final approach—GCAs are no longer in widespread use at civilian airports, and are being discontinued at many military bases.However, air traffic controllers at some locations in the United States are required to maintain currency in their use, while the Belgian Air Force still uses the PAR for ground-controlled approaches on a daily basis.