Final answer:
An application for a special flight permit in an emergency can be made online, through a website or a digital portal managed by the aviation authority.
Step-by-step explanation:
In case of emergency, an application for a special flight permit can be made via online machine. The correct answer is option d: online. This process is part of civil aviation regulations and is typically facilitated by the aviation authority in a given country. For instance, the Federal Aviation Administration (FAA) in the United States might allow pilots or aircraft operators to apply for these permits through a website or a digital portal designed to handle such requests. Applications for special flight permits are necessary when an aircraft does not meet airworthiness requirements but still needs to fly for specific purposes, such as to a location where repairs can be made.