This paper proposes a simulation structure for aeronautical wideband frequency - selective channel, which features ground - air and air - air wireless links. With appropriate channel parameters, the channel emulators of the parking, taxi and en-route states can be modeled in frequency domain. The wideband frequency-selective channel consists of some parallel sub-channels in frequency domain, which are assumed to be independent to each other and have Rayleigh - distributed envelopes. The sub-channel models and emulators are based on a simple structure and characterized by flat fading. Through such decomposition approach, a frequency domain frequency - selective channel model can be achieved, which is suitable for an implementation of orthogonal frequency - division multiplexing (OFDM) or multi-carrier code - division multi-access channel emulator.