If that scan is correct even a filter can’t help you.
Somehow you are getting strong noise from 1060 to 1120 MHz.
(The filter can’t filter 1090 MHz and a little bit around that otherwise it will filter the airplanes as well)
The only question is where the noise is coming from because it’s obviously less of a problem with your indoor antenna.
Maybe the cable is going by some very strong RF noise?
(That much noise would mean somehow the coax you are using is not shielded properly)
I suppose you could use gqrx to display the spectrum/waterfall live, tune for 1090 MHz and move around with your laptop and walk around a bit, maybe you can make out a source.
Or walk around with the FA antenna.
Apart from that you might have noticed additional to the options for filters from my previous post, FA is selling a new filter (which is better than the old one): Announcing the new 1090 MHz only bandpass filter!