The FAA, which is responsible for the regulation of air carriers, holds commercial airlines to quite rigorous standards of care for their passengers. While the complete safety of passengers cannot be guaranteed, negligence in any form is the responsibility of the airline. That is, while an injury is not proof of negligence or fault, airlines must make every reasonable effort to prevent injuries from occurring.
From the moment the plane is boarded until the passengers have disembarked, the airline may be liable for any injuries that occur; the plane does not need to be in the air at the time the injury occurs. In-flight injuries can vary considerably in their degree of seriousness; from twisted ankles to concussions, both minor and major injuries are possible. Turbulence is the leading cause of in-flight injury. Because of this, wearing one’s seatbelt is essential to safety. Failure to wear a seatbelt or to obey the directions of the crew may seriously undermine a claim against an airline. Furthermore, airlines may not be held liable for unforeseeable events, such as turbulence that was not possible to anticipate. Pilots are, however, responsible to check the weather and to delay or alter flights if weather conditions are not favorable.
The only solid basis for a claim against an airline is human error. Airlines are required to ensure that the operation, inspection, repair, loading, and boarding of a plane are carried out properly. Aisles should be clear, routes to exits and bathrooms should be safe, cabins should not be overloaded, and any equipment should be in safe and working condition. Failure in these and other areas may be grounds for a lawsuit.
The airline and its personnel may not be the only parties at fault for an in-flight injury. Malfunctions or errors may be partially or entirely the fault of the manufacturer, seller, or repairer of the aircraft or its equipment. Furthermore, Air Traffic Control (ATC) is responsible to alert the pilot if they become aware of a dangerous situation and my be liable for damages if they fail to do so.