Delaware has very favourable laws for taxation of corporate income and for ease of company formation and management. It also has very predictable business law. So it's a favourite for corporations which trade, have income, have shareholders, own complex assets, etc. For a company with few or no shareholders whose sole purpose is to own an aircraft, or for a trust, there are other places in the USA that are also favourable. Delaware is the firm favourite for "real companies", but plastic fake companies have several good homes to choose from.