India is a member of MCTR now, we can remove the limitations we had on our ballistic ans hypersonic missiles. 700-900km range or more can be implemented now.Brahmos Aka Oniks of Russia , always had 600km range. Was limited by software to comply with international laws.
Additional 200km are gained by firing from Altitude in air launch.
The launch altitude has to be significant to have this additional range
Firing from lower altitude will have lesser range.