This document provides guidance for laser operators and aviation authorities to determine the performance criteria that laser hazard control measures shall meet for the operation of an outdoor laser system in navigable airspace. The document does not cover systems intended to deliberately aim and or track lasers at aircraft except for FAA approved purposes, such as visual warning systems, search and rescue, etc. Aircraft operations to be protected include all types that can be reasonably expected to operate in the affected area, which are traveling at speeds and altitudes defined in the Performance/Functional Requirements section. This document does not address all possible aircraft operations, (e.g. the operation of stealth, high-speed (> Mach 1), unmanned aircraft systems, aircraft above 60 000 feet MSL, etc.), including aircraft operating under a waiver from FAA regulations. Depending on the laser system's location and operational characteristics, the proponent may be required to coordinate with local military facilities and with the USAF Space Command. The military may request additional requirements (such as limitations on lasing hours or locations), or they may take actions to avoid the laser location. Operators of lasers outdoors must show that the laser hazard control measures used to prevent aircraft illuminations are adequate in order to ensure aviation safety and receive a letter of non-objection from the FAA. Historically, control measures have included the use of safety observers to monitor for aircraft and, in many applications, the use of safety observers is an effective control measure. In other situations, the use of alternate control measures may provide additional safety and may be more cost effective. For example, the use of safety observers can be expensive and, in remote and environmentally challenging locations, it can be difficult to find and retain enough qualified people willing to do this type of work. The cost for safety observers to support 140 full nights of laser operations per year at W. M. Keck Observatory on Mauna Kea, Hawaii is about $300,000, and the site is several miles away from cities and towns. With the addition of 3 other facilities on Mauna Kea that will routinely use lasers in their operations, the total cost for safety observers may be over $1,000,000/year and the number of safety observers needed may exceed the supply in the local population. In addition to cost considerations, the effectiveness of safety observers in spotting aircraft is limited relative to the hazard distances of some lasers. To address the provision of safety at these distances, additional means to detect aircraft are needed to supplement or to replace the safety observer.