MBA/PGDM

More details: https://admissionblock.com/
In the year 2018 students of PES University, Bangalore got direct campus placements in top companies like Infosys, Wipro, TCS, IBM, Accenture and more. Students of PES University, Bangalore got the highest package offer of Rs 8 Lacs per annum and an average package of Rs 6 Lacs per annum.

More details: https://admissionblock.com/
Yes, candidates need to appear for PESSAT which is an All India Online Entrance Exam for admissions into various programmes offered by PES University including MBA. Candidates can secure admissions into programmes such as B.Tech, BBA in Hotel and Event Management, M.Tech, MBA, MCA M.Sc in Engineering by clearing PESSAT 2018.

It depends totally on the college that what criteria they set for the admissions. But if you have scored more then 50% you can get admission in any good colleges.
More details click here : https://admissionblock.com

You can choose any field in MBA if you are interested in.
But as you are interested in a mechanical engineering related field, go for Operations Management as they are dealing with the production, quality and supply chain in the industrial area.

I will suggest you go for both of those exams as CAT and MAT are the entrance exams preferred by most of the MBA colleges. If you perform well in at least one exam, there are very good chances of getting a good college. The syllabus for both the exams is not that different.

Yes, Narsee Monjee is a good option. You can also do some research on distance MBA programs of Welingkar Institute in Mumbai and Symbiosis in Pune.

No, MBA course is available in English only and that should be in English as English is an important language for any managerial job.

If you are getting any top-reputed college through UPSEE, then go for it as you already have a good rank.
Don't waste one year for CAT and MAT. That would be a risk if you do not score well.

MBA is a post graduate programme. So, you first need to complete your graduation and then look for admission in MBA in Aviation. Since you are interested in Aviation you could also explore B.Sc. in Aviation & then go beyond.