Consider some background information. To operate a particular type of airplane for the first time, the FAA requires the airline to demonstrate an evacuation in 90 seconds, using only half the available emergency exits while simulating the ambient light equivalent of night darkness. To prevent injuries to volunteers during the demonstration, the FAA considers computer analysis in some circumstances. And sometimes within a family of similar aircraft, i.e., in the Airbus A320, 319 and 318, a partial evacuation is allowed that involves just the cabin crew and no passengers. The partial demonstration must be completed in 15 seconds and must include the operation of the emergency exits and slides. These evacuation drills are completed in mostly ideal conditions: an intact and level airplane, an intact and handpicked cabin crew, operative emergency equipment, relatively knowledgeable passenger volunteers, and a scenario already anticipated.