This paper presents two infrared laser spectrometers built to measure CH4, N2O and CO stratospheric concentrations. Both TDL were designed as a subsystem of a composite airborne instruments package, devoted to the chemical and microphysical diagnostics of stratospheric aerosols, developed in the frame of the Airborne Platform for Earth-observation programme (APE). We present the results of the measurements of N2O and CH4 concentration in the stratosphere performed in a polar campaign on board of the Geophysica M55 aircraft.