Federal rules dictate how close together aircraft are allowed to fly. An incident involving three aircraft around Ronald Reagan National Airport in Washington D.C. has prompted an FAA investigation, according to Transportation Secretary Ray LaHood. Early reports indicated that the planes were on a head-to-head course, but Mr. LaHood and FAA administrator Michael Huerta indicated that while "there was a loss of separation" among the aircraft, they were never on a collision course.
According to federal guidelines, commercial jets should have at least 3.5 miles between them horizontally and 1,000 vertically. In the incident in question, a plane that was landing had 800 feet of clearance vertically and less than 1 mile horizontally from a plane that was taking off. The landing plane was within 800 vertical feet and 2.4 miles laterally from a third plane. Officials had changed the directions of the planes to compensate for a storm. Mr. Huerta reported that the planes were on different headings and were all at different altitudes, so while federal guidelines were violated, the planes would not have hit one another.
Air traffic controller conduct has been a source of concern among safety officials recently. The National Transportation Safety Board listed pilot and air traffic controller professionalism on its Most Wanted List of advocacy priorities in 2012. The NTSB has made several recommendations regarding performance monitoring and proper standards of performance for air traffic controllers. The Transportation Secretary indicated that the FAA intended to take all appropriate action at the conclusion of the investigation.
Source: Los Angeles Times, "US Airways planes were not on collision course, FAA chief says," by Michael Muskal, 2 August 2012