Abstract: Identifying the main sound sources under typical aircraft operating status and estimating their radiated sound power are of great significance for aircraft low-noise design and noise pollution assessment. In this study, a beamforming algorithm is employed to develop a method that utilizes a sound array to identify the external main airframe sound sources and estimate their radiated sound power levels during both aircraft ground operation and low-altitude flight. Additionally, a method for analyzing the contribution of these main sound sources is proposed. A flight test technical plan is then presented, which centers around the measurement of sound–aircraft–environment parameters. The proposed methods are validated through a series of sound tests conducted on a fighter plane and a large transport aircraft, utilizing a well-designed non-uniform linear acoustic array and a planar multi-arm spiral acoustic array. The results demonstrate the efficacy of the proposed methods in accurately identifying the main sound sources within the frequency range of 200–2000 Hz, as well as estimating the radiated sound power levels of the aircraft engine and airframe sound sources, thereby enabling the determination of their respective contributions to the overall sound power.