What must be maintained in the aircraft logbook according to Federal Aviation Regulations?

The correct answer focuses on the maintenance, inspections, and airworthiness directives compliance, which are crucial for ensuring the safety and airworthiness of an aircraft. According to Federal Aviation Regulations, aircraft logbooks must include detailed records of all maintenance performed on the aircraft, inspections conducted (including annual and progressive inspections), and compliance with any airworthiness directives issued by the Federal Aviation Administration (FAA).

These records serve several important purposes: they provide a documented history of the aircraft's maintenance, help verify that it meets regulatory requirements, and ensure that any necessary repairs or modifications have been properly executed. This information is essential not only for regulatory compliance but also for the safety of the aircraft and its operation.

In contrast, while flight crew certifications and passenger manifests are important for operational purposes, they are not required to be maintained in the aircraft logbook itself. Weather condition reports, while relevant for flight operations, are also not a component that must be documented within the aircraft's logbook under the regulations. Thus, the emphasis on maintenance and inspections is what makes the second choice the correct response in this context.