Recent investigations carried out at the Laboratory of Optical Physics,Institute of Physics,CAS,on the propagation of intense femtosecond laser pulses in air is presented. A long-distance plasma channel is formed with a length of several hundreds meters. Four methods are developed to diagnose the plasma channel. Strong third harmonic emission is observed with a maximum conversion efficiency of 0.3%. The filaments distribution is optimized for applications using a pinhole with different diameters. The lifetime of the plasma channel is prolonged up to the order of microsecond. The filamentation process and the surpercontinuum emission are closely related with the initial chirp of the laser pulse. Triggering and guiding of large gap discharges in air by plasma channels opens promising perspectives for lightning control.