A program of searching for and analysing a rapid profile variability of bright O supergiants with time resolution 5-30 minutes is descri\-bed. Preliminary results of spectral observations of stars lambda Ori, alpha Cam and 19 Cep with the 1 m telescope of Special Astrophysical Observatory are presented. A variability of line profiles in the spectra of all studied stars is detected. The variability of Halpha and CIII lambda 5696 lines in the spectra of lambda Ori is detected for the first time. The amplitudes of variable details of the line profiles are 4-5% for 19 Cep and 1-2\% for alpha Cam ¨ lambdaOri at the time scale from a few hours for alpha Cam and 3-4 days for lambda Ori A. The widths of the variable details are up to 2-4 \AA (100 km/s). The cyclical profile variations of HeII lambda 4686 and CIII lambda 5696 lines in the spectra of lambda Ori A with the recurrence time of 1.3-1.6 days are detected. The fast variations in the violet parts of the Halpha and HeI lambda 4713 lines in the spectra of lambda Ori A with the recurrence time in a range 3.5 -7^h are found.