No part of an aircraft is 100% reliable. Manual inspections are a fundamental part of keeping an aircraft safe. How do you know that the tires haven't perished? How do you know that a bulkhead isn't developing severe stress cracks? How do you know that the bearings on a control surface aren't just about ready to seize? Because the aircraft operator is required by law to systematically check every part of the aircraft according to a strict schedule.

Your reassurance is the fact that flying is the safest form of travel thanks to decades of diligent work by engineers, mechanics and accident investigators.