It's worth remembering that commercial aerials may not work as well as homebrew ones.
My two element J-pole in the loft receives almost as many aircraft/day as the FlightAware stick which is mounted outside and about ten ft higher, the main difference is the number of reports received/day. The external one receives a lot more.
Taking from the FA stats.
My internal receiver sees an average of 3,156 aircraft and 805,679 positions per day
My external receiver sees an average of 3,213 aircraft and 950,992 positions per day
(yes, I know that's a lot - My receivers generally sit in the top three in the UK FA charts, currently at positions 2 and 3).
If I could be bothered to fully weatherproof my internal aerial and mount it externally, I think it would probably outperform the FA stick.
Coax is important - The longer the run, the more the loss. My internal receiver is connected directly the the aerial and the external one has less than a foot of cable.
Here's my external receiver heatmap from Planefinder.