What is required for filing a flight plan to Canada from the contiguous US?

When filing a flight plan to Canada from the contiguous United States, the use of DD Form 175 is correct because this form is specifically designed for military or official government flights and is commonly used in the planning stages of a flight. In a more general aviation context, the Standard Flight Plan form (which can be similar to DD Form 175) is also utilized to provide necessary information such as route, departure, destination, and the estimated time of arrival, fulfilling legal and safety requirements for international flights.

The other options are more specific to different contexts; for example, DD Form 1801 generally pertains to moving military cargo, whereas weather verification documents and flight maintenance records, while important for safe operations, are not part of the required documentation for filing a flight plan. Therefore, the use of DD Form 175 is the key requirement for submitting a flight plan to Canada.