Copilots are an essential part of any flight crew, but there are various synonyms that can be used to describe these roles. The term "second-in-command" is commonly used in aviation and denotes the copilot's position as the assistant to the pilot in charge. Alternatively, the copilot can be referred to as the "first officer." This term is often used in commercial aviation to differentiate between the captain and the copilot. Another synonym is "co-pilot," which is a shortened version of copilot, but maintains the same meaning. Ultimately, regardless of how they're described, all of these terms refer to the individual working alongside the captain to ensure a safe and successful flight.