Airplanes have very particular maintenance schedules. Some things are based on the amount of hours flown, others are calendar items on a set schedule. They are also periodically stripped down completely to check every last part.

Basically, every critical component on it will have been recently replaced, overhauled or checked. If done correctly, a 50 year old plane is not inherently more dangerous because of its age. The caveat to that being: if it’s done properly.