A new chemical measurement system for reliable, simultaneous, high frequency measurements of ozone, nitrogen oxides, carbon monoxide and carbon dioxide for the calculation of turbulent trace gas fluxes by eddy-correlation technique is developed. The system is optimized for the research aircraft Dornier 128-6 (D-IBUF), but can also be used on ground or aboard other aircrafts. Trace gas concentrations are measured with analyzers modified to fit aircraft conditions and a system built using commercially available components. The special gas distribution system prevents contamination, minimizes concentration losses and provides air to all analyzers with adequate flow and pressure. New calibration strategies and the development of a computer controlled nitrogen oxide calibrator are basis for the very high measurement accuracy with has been proven during independent international QA/QC Programs. Correction procedures for signal delay caused by the gas distribution, sensor delay and flight attitude are developed. Using vertical wind velocity data from the aircraft measurement system turbulent fluxes are calculated by eddy-correlation method. Covariance spectra of trace gases and vertical wind velocity together with those of different trace gas species can be used to separate transport processes and chemical reactions, to identify typical scales and to quantify fluxes by integration.