When are Basic Postflight Inspection (BPO) inspections conducted?

The correct answer is that Basic Postflight Inspection (BPO) inspections are conducted after the last flight of the day. This timing is crucial as it allows personnel to assess the aircraft's condition at the end of its operational day, identifying any issues or wear that may have occurred during its flights. By completing the inspection after the last flight, maintenance teams can ensure the aircraft is safe and ready for subsequent operations, maintaining safety standards and operational readiness.

Conducting the inspection at this time also supports effective maintenance scheduling, as any findings can be addressed before the aircraft is used again. It is an important procedure to ensure that any discrepancies can be documented, and necessary repairs are made to enhance safety before the next set of flights.

The other options imply timing that either doesn't afford the same level of ongoing monitoring after operations or suggest additional inspections that might not be required or practical. For example, inspections before the first flight, or nightly inspections don't capture the immediate state of the aircraft right after it has been used, which is what the BPO is designed to assess.