Most airlines typically try to purchase their fleet all from the same manufacturer if they can.

There's a lot of additional cost that goes into maintenance, pilot training, pilot availability, etc. that has to be accounted for if you're mixing aircraft from different manufacturers.

You can just look up the aircraft owned by an airline and it will give you a pretty good idea what to expect.

You can also go on flight tracker sites and just look at what aircraft are running the route currently, which would also be a good indicator.