Ever wondered how aircraft stay safe and operational? Aircraft undergo periodic maintenance checks to ensure their safety and efficiency. These checks, often referred to as A, B, C, and D checks, range from basic inspections to comprehensive overhauls. The D check, also known as the heavy maintenance visit, is the most thorough, taking the entire airplane apart for inspection. This intensive check can take up to 50,000 man hours and is performed approximately every six to 10 years. Due to its complexity and cost, airlines plan D checks years in advance. Interestingly, an aircraft usually undergoes only two or three D checks before retirement. These maintenance routines play a crucial role in ensuring the safety of millions of passengers flying daily. Stay sharp with TL.