Which dongle are you using?
The pro stick plus has an internal filter that cuts quite some of that 900 MHz band but it is still stronger than the 1090MHz band. (Which is expected since the transmitters of aircraft are less powerful and further away than the mobile towers)
Have a look at this post if you are looking at getting another filter:
Please not that while the rlt-sdr lna improved my reception the reception was quite good with the pro stick and filter.
The signal does not need to be eliminated just weakened sufficiently that it interferes less 