Disclosed is a method for maintaining a level of operational reliability for aeronautical equipment in compliance with the requirements for safety and regularity of flights. According to the method, technological operations, which are basic for the stages of assembling, erecting, ground and flight testing, are carried out sequentially during some period of time. During the assembling stage final modules, units and systems are assembled with the use of individual parts delivered from the pre-assembling area then the assembled module or unit is checked for its completeness and technical condition. The above-mentioned modules and units are checked for absence of foreign objects in cavities then they are tested and adjusted. During the erecting stage a complete set of required parts is installed, then hatches, some panels and floors are opened, the whole fuselage and each erection area are cleaned and washed, inner spaces in fixed fuel pipelines and fluid systems are washed; a fit of pipelines in connections and to the aircraft board is checked, the erection areas are inspected; after inspection the units and assemblies are installed and fastened, communication lines are laid and fastened, the components are connected, all system are optimized and adjusted; before installation the parts, modules or units are subjected to incoming control be means of inspection; after completion of the erection work and checks of their quality testing the system operability begins that is the system functioning is checked. After testing operability the systems are adjusted and optimized then troubleshooting is carried out by means of comprehensive inspection; if no foreign objects are present and after removal of revealed defects all hatches and floors are closed; after completion of the erection stage the aircraft is leveled; after completion of the leveling the aircraft is weighed and its center of gravity is determined; after weighing the execution of the program of ground and fight tests begins. During the stage of ground tests the quality of the performed repair work is checked and the operation of all onboard systems is evaluated and, if required, their parameters are adjusted until their compliance with the specifications. During the stage of flight tests the pilots and other members of the crew appointed for testing the aircraft under conditions of the specified flight route carry out preliminary inspection; after that the operability of the control system is checked, the engines are started, the systems of aeronautical and avionics equipment are checked and the flight tests themselves are carried out; at that all assembling works are carried out in accordance with the assembling chart, the assembled fluid systems are tested for tightness and operability with the use of the ground power sources, the completeness of the erecting/ assembling works is ensured with the use of schedules and according to the sequence of their execution, the physical parameters are checked after finishing the erection works. During the ground tests the quality of the erection works for the onboard systems, the landing gear, the aeronautical and avionics equipment is fully inspected. During the flight tests before the flights begin. deviations (corrections for magnetic variations in navigation instruments) are made; after that the ground taxi operation of the aircraft is carried out for checking the efficiency of the brake operation. After completion of the flight tests and removal of revealed defects the repaired aircraft is handed over to the customer. When the landing gear is ground tested, pressure in the shock struts and wheel tires is checked; after filling up the hydraulic system from the test stand the gear retraction and extension operations are checked with registration of manometer indications and time spans required for these operations, the signals that indicate the retracted or extended positions of the landing gear as well as the pressure in the brake system are checked; for the hydraulic system a charge is checked and the purity of the working fluid is determined by sampling; for the aircraft and engine control systems the operability of all systems is checked and the operation time is determined at that all indications of the instruments and signaling systems are recorded; for the fuel system the correspondence between the fuel availability indications of the onboard indicators and the actual data from the ground refuelers is checked, the performance of the pumps and taps is evaluated, the signals of minimum amounts of remaining fuel as well as other parameters are checked; for the aircraft's power units the engine control system is checked, the engine are started, and the starting equipment is checked, under conditions of the automatic start the time of starting engines and attaining their corresponding modes of operation is evaluated at that all operating parameters of the engines (speed, temperature) are recorded; for other onboard systems of the aircraft the operation of control equipment and units is checked, the operation time and other parameters are recorded; for the aeronautical and avionics equipment the operability, the absence of interferences, the quality of signal detection and transmission are checked, the values of pressure, voltage, current, flow rates, response time and other parameters are adjusted; after performing adjustment and adjustment quality control all working areas are cleaned and washed, all hatches and panels are closed, floors are installed and the bore-sighting of the aircraft weapon is carried out; then the complete set of design plans and specifications fo the ground tests is developed. During the flight tests the aircraft is loaded according to the loading chart, the load is arranged in accordance with the service conditions under which the aircraft is operated; during the flight tests the aircraft systems (the control, fuel, hydraulic, pneumatic, air-conditioning and de-icing systems) are checked, at that during the assembling stage when the aircraft fluid systems are checked all standard filters are replaced by the pilot ones, before starting the erection works the availability of power sources at the aircraft is checked, lighting fixtures which ensure sufficient illumination of the erection areas are installed, the cabin floor is covered with working panels, large-dimension units are erected when their weights are fully relieved, the aircraft is leveled when it is fully assembled, its landing gear is extended and it is installed along the flight line on hydraulic lifts; for the aircraft and engine control systems the works on checking the operability of all systems are performed two times, when they are powered from a ground power source and when they are powered from the onboard source while the engines are operated; when testing the engines the positions of the engine's guide vane limbs are visually controlled in order to make a decision on adjustments in the operation of the above-mentioned engine, when conducting the visual control over the positions of the engine's guide vane limbs an optic-TV surveillance system is used. During the ground tests the aircraft fuel system is entirely filled and occurrence of leaks or sweating points is checked; for testing on leaks and sweating points special additives that glow under exposure of light in a specified wave range; for bore sighting a device that is installed on a weapon object is used, the device designates an aiming mark with the use of a laser beam; for ground taxi operations as a rule a non-linear (with turns) path of motion is chosen in order to perform a more comprehensive test; during the flight tests the flight and trim characteristics, the aircraft stability and sensitivity are checked.