IntroductionLaser illuminations of aircraft in navigable airspace have concerned the aviation community for over a decade. The principal apprehension is the effect laser illumination may have on flight crew personnel performing landing and departure maneuvers, where procedural requirements are critical. This study examines the frequency of aviation-related laser incidents by altitude of occurrence. MethodsEvent reports of aircraft illuminated by high-intensity light sources have been collected from various sources and entered into a database maintained by the Federal Aviation Administration's Civil Aerospace Medical Institute. Reported events of laser exposure of civilian aircraft for a 5-year period (January 1, 2004 to December 31, 2008) were collated and analyzed. ResultsA total of 2,492 laser events occurred in the U.S. during the study period. The cockpit environment was illuminated by laser beam in 1,676 (67.3%) events, and altitude information was provided in 1,361 (81.2%) of these reports. At altitude levels associated with the FAA's Laser-Free Zone (0-2,000 feet), cockpit illuminations increased from 12.5% to 26.7% for the period, while the percentage for Critical Flight Zone equivalent altitudes (>2,000-10,000 feet) decreased from 87.5% to 58.4%. For the period, green laser light was reported in 92% of the events where color was identified. ConclusionThe increasing percentage of aircraft laser illuminations reported at or below 2,000 feet that involve green laser light may represent an escalating threat to aviation safety. Low-flying aircraft, which may not be within currently established flight hazard zones around airports, need protection due to their increased vulnerability to laser illumination and their close proximity to obstacles and terrain.