Let's say you take a plane.
In your schedule, you will have one stop at an airport to change to the second plane.

I will be in transit at SFO airport.
I will make a transfer at SFO airport

Not sure which one sounds better. Thank you.
I would not use either of those. Here's what I say:

I (have to) change planes at the San Francisco airport.
I (have to) change planes at SFO.

Students: Are you brave enough to let our tutors analyse your pronunciation?
I didn't know it was as simple as that!

By the way, that makes me want to know in which context we will use 'in transit' and 'make transfer'?

Thank you.
Nor Priest'in transit'
I use this to mean 'on the way', 'traveling'.

The main office has sent us the documents, but we haven't received them yet. They are still in transit.
Nor Priest'make transfer'
I don't use this. I just say 'transfer' to mean 'move from one place to another'. The meaning need not be literal.

To get to our destination, we had to transfer from a bus to the subway.
After two years at Junior College, Steve transferred to the University of Michigan.