The designer's problem is trying to anticipate the possible stresses that the structure will have to endure, and to build it sufficiently strong to withstand these. The problem is complicated by the fact that an airplane structure must be light as well as strong. The manufacturer states upon certification that the design meets or exceeds all FAR requirements for the category of aircraft being produced. However, hard landings, gust loads caused by extreme turbulence, performing aerobatic maneuvers in a non-aerobatic airplane, etc,. can affect the airworthiness of one or more major airframe assemblies to the extent that the airplane is no longer airworthy. This reiterates the necessity of operating the aircraft within the limitations outlined by the manufacturer.
Every flight imposes loads and stresses on the aircraft.
How carefully it is flown, therefore, will have an effect on the service life of its assemblies. It is the UFO's ability to withstand or defy the normal loads and stresses of our conventional aircraft that allows them to fly in such erratic modes as zigzag flight, instantaneous decelerations, and instantaneous accelerations. The type of flight pattern makes a UFO stand out from the aerobatic performances of conventional aircraft. This is only a small part of a subject that could fill a textbook. It is by capturing these details of UFO flight dynamics for the record that adds weight to the evidence that unconventional flying objects have been cavorting around the earth for decades.