firing CMs from well within our territory is just as much safer. gurus can shed more light on the advantages of firing from Air but i think firing a salvo from air on specific targets with better visibility, reach and targetting would be some of the benefits. The IAF wants air launched brahmos.
some time back , i read that ,if a country is going to war then the following sequence of attacks takes place
1-Land launched cruise missile to destroy known enemy SAM station ,ammunition dump and other vital targets
2-Recon mission by aircraft (entering enemy area to limited extent ) and followed by other destruction of enemy site
3-Air dominance and destruction of airfields ( done by air launched cruise missiles)
5-Brining in strategic bombers to finish the rest of the job
now since Stealth aircraft are around these can do the initial bombing raid to destroy the SAM sities