In a 6-7-10 amendment, which element must field 10 begin with?

In a 6-7-10 amendment, field 10 must begin with the route's element separator. This separator is crucial for the proper interpretation and processing of the routing information. It serves as a marker that delineates different components of the flight plan, ensuring that each part is correctly identified and parsed by air traffic control systems.

The route's element separator helps maintain the structure and clarity of the data transmitted, allowing for efficient communication between pilots and air traffic controllers. This clarity is paramount in the aviation industry where misunderstandings can lead to serious safety issues. Without a correct starting point, the entire routing information could be misinterpreted.

Options like the aircraft identifier and current altitude, while important components in the overall flight information, are not the starting element of field 10 in this specific context. Instead, they would occupy their own respective fields as defined by the amendment's structure. The previous field data is also not relevant since it pertains to information that has been processed before field 10, rather than being a foundational element of it.