Can we apply for mtech in aerospace engineering after doing btech in information technology
Good Luck

But before changing the branch, you must be 100% sure about your future . Because in India there are very limited colleges such as IITs and NITs which offers you admission. So in future you may face lots of problem to join in Industry because your resume will completely change after your M-tech. Then only option remains for you after M-tech is to join for lectureship or PhD.
Some of my friends have joined for lectureship in private engineering colleges after their M-tech in Aerospace. They didt get any entry in Industry as trainee.
Thanks,
Azim