Mass Frontier allows the extraction of the average mass spectrum from several scans. To do so click the Spectra Average button  and then mark off the region of the scans that should be averaged by dragging a rectangle around the region. The marked region will be displayed in the same color as the active scan line (by default purple). The average spectrum will be displayed in the Scan tab. To cancel the spectra average mode, just click anywhere in the chromatogram pane and the single scan mode will be restored.