A type certificate signifies the airworthiness of a particular category of aircraft, according to its manufacturing design (type design). Certification confirms that the aircraft of a new type intended for serial production, is in compliance with applicable airworthiness requirements established by the national air law. For up to three seats, primary category aircraft certification costs around US$1m, US$25m for a general aviation aircraft and hundreds of millions of dollars for a commercial aircraft; certification delays can cost millions of dollars and can decide a program's profitability. Authority A type certificate (TC) is issued to signify the airworthiness of the approved design or "type" of an aircraft to be manufactured. The TC is issued by a regulatory authority, and once issued, the design cannot be changed unless at least part of the process for certification is repeated to cover the changes. The TC reflects a determination made by a regulatory authority that the type design is in compliance with airworthiness requirements. Examples of regulatory authorities are the U.S. Federal Aviation Administration (FAA), the European Aviation Safety Agency (EASA), Transport Canada, Brazil’s Agência Nacional de Aviação Civil and the Civil Aviation Administration of China (CAAC). When changes are needed to an airframe or on-board equipment, there are two options. One is to initiate a modification by the type design holder (manufacturer), and the other is to request a third party Supplemental type certificate (STC). The choice is determined by considering whether or not the change constitutes a new design (i.e. introduces risk not considered in the first type design). If so, then type design holder must develop and approve a modification to the type design. If the regulatory authority agrees the change does not introduce new risk, the STC option is available. An STC is less expensive because the design change can be developed by a specialized design organization, a generally more flexible and efficient process than going through the original manufacturer. The STC defines the product design change, states how the modification affects the existing type design, and lists serial numbers of the aircraft affected. It also identifies the certification basis for regulatory compliance for the design change. The TC implies that aircraft manufactured according to the approved design can be issued an airworthiness certificate. To meet those requirements the aircraft and each sub-assembly must also be approved. For example, in the U.S. these sub-assemblies must meet requirements in the applicable