Washington D.C. area air-traffic controllers made a record number of mistakes in 2010, joining a nationwide trend of an increase of 51 percent more errors. Mistakes made by air-traffic controllers can cause collisions and close calls. The Potomac Terminal Radar Approach Control Center, the control facility for the Washington area, recorded its 52nd error on Christmas Eve when two Southwest Airlines 737s approached Baltimore-Washington International Marshall Airport on convergent courses. The Federal Aviation Administration said in a statement Thursday that a new system of recording errors had been adopted, and resulted in a higher number of reported incidents. But the FAA and the reorganized controllers’ union admitted this doesn't account for the huge increase.