AMS 2680 covers electron beam welding in fatigue-critical applications. The standard specifies that all welds be full-penetration welds to avoid stress concentrations and that procedures are designed to minimize porosity and other weld defects. It is the standard used for welds when “the failure of which could cause loss of the aerospace vehicle or one of its major components, loss of control, or significant injury to occupants of a manned aerospace vehicle, but usage is not limited to such applications. It covers requirements such as the vacuum level required for welding, specifics of non-destructive testing, and the acceptable amounts of defects like underfill and undercut.