Eligibility Criteria, Varies across Universities and Higher Technical Institutes. However nowadays as far as IITs, NITs and IISc Bangalore is concerned, they have somewhat relaxed the Admission Criteria. Besides BTech in Production, Materials or Mechanical, you may require GATE Score for Aerospace, to secure a seat in MTech. However you should check the Elgibility Criteria for your Target Universities before deciding on apper for GATE or pursuing MTech in Aerospace.

For further reference, you may check IISc Bangalore's Admission for MTech Aerospace do follow the link below

https://www.careers360.com/university/indian-institute-of-science-bangalore/mtech-aerospace-engineering-course