The performance of mixed Free Space Optical (FSO)/Radio Frequency(RF) airborne communication system based on amplify-and-forward 2×2 relaying is analyzed in the paper. The Nakagami-m fading channel is adopted for RF communication link and the FSO link undergoes the Exponentiated Weibull fading channel. The 2×2 relay-assisted mixed FSO/RF airborne communication system is established and the closed form expressions of probability density function (PDF) and cumulative distribution function (CDF) about equivalent signal-to-noise ratio(SNR) are derived by Meijer′s G function. Moreover,the expressions o average bit-error-rate and outage probability are obtained. The relationship between the BER performance and the SNR under different parameters such as the atmosphere turbulence,aperture size and modulation scheme are analyzed by simulation.