Hello Aspirant,

IIST offers the Undergraduate programmes as below

4-Year B.Tech. ( Aerospace Engineering )
4-Year B.Tech. (Electronics and Communication Engineering (Avionics))
5-Year Dual Degree (B.Tech. + Master of Science/Master of Technology)

As per the eligibility, Candidates must have secured at least 75%  aggregate  marks  in  the  Class  XII  (orequivalent–  Qualifying Examinations) Board examination. The aggregate marks for SC, ST and PDcandidates should be at  least  65%.

The  marks  scored  in  the  following  five  subjects  will  be  considered  for calculating the aggregate marks: Physics, Chemistry, Mathematics, A  language  (if  the  candidate  has  taken  more  than  one  language,  then  the  language with the higher marks will be considered), Any  subject  other  than  the  above  four  (the  subject  with  the  highest  marks  will  be considered)

You can check the further information to go through with the given below link.

https://www.iist.ac.in/sites/default/files/admissions/UG-Admission-2019-Information-Brochure-15May2019(2).pdf

Good Luck!