Flying machines such as aircraft and helicopters face high failure risks, and these risks include failure of engine, fuel system, structural failure, systems failure, and other types of failures (Kinnison Siddiqui, 2012, p. 3). To ensure that only airworthy aircraft can fly, The Federal Aviation Administration – FAA, a US government body that oversees commercial aviation safety in the US, has provided a number of guidelines and regulations concerning the maintenance and overhaul of all types of aircraft. These are covered under the program continued analysis and surveillance system – CASS. Each aircraft manufacturer provides its own maintenance schedule, the Air Carrier Maintenance Program, for each model of aircraft, and the FAA regulations support these regulations (FAR/AIM, 2012, p. 12-14). This paper examines two important elements of this program and discusses several important subjects on maintenance.The main types of maintenance are routine and preventive maintenance and hard-time maintenance. Routine and preventive maintenance involves cleaning, changing the oil, changing filters, and activities, where the full engine and critical components of the engine, propeller, landing, are examined from the outside for any oil leakage, or abnormal sound (Kinnison Siddiqui, 2012, p. 6). Hard-time maintenance involves dismantling the engine, landing gear and other critical components, examining important components for excessive wear, scoring or discoloration that would lead to progressive failure, and replacing the components (Crane, 2012, p. 56-57). Many critical components of aircraft have a specified life, measured in flying hours. After an aircraft flies for the designated number of hours called the retirement hours, these components are replaced, even if they are not damaged. Each major part of an aircraft has a unique part number and a service life. Workshops need to maintain a logbook that records the number of hours flown by the machine, the parts serviced, and replaced (Schafer, 2006, p. 131-134).