FSX uses only default aircraft, to hide them so you don't see them in your menus rename the panel folder of the aircraft you want to hide to
panel=HIDDEN or if you need the panel for another that you do want, you can rem out the entry in the aircraft config file
FSINN does use the aircraft and if you don't have it tries to find one that is close
here is an example of the A321, add the 2 // to hide the plane from menus or panel=HIDDEN
to hide from menus and still let FSX use the aircraft
// [fltsim.0]
title=Airbus A321 D2013
sim=Airbus_A321
model=
panel=HIDDEN
sound=
texture=2
kb_checklists=AirbusA321_check
kb_reference=AirbusA321_ref
atc_id=
atc_airline=Canadian
atc_parking_types=GATE
atc_parking_codes=
atc_flight_number=
ui_manufacturer="Airbus"
ui_type="A321"
ui_variation="World Travel Airlines"
ui_typerole="Commercial Airliner"
ui_createdby="Microsoft Corporation"
description="The Airbus A321 is a stretched version of Airbus’ best-selling short- and medium-range A320. The A321 has a slightly increased wing area, stronger landing gear with larger tires, and engines with increased thrust. When the A321 entered service in 1988, it pioneered the use of “glass cockpit” instrumentation, the first digital fly-by-wire control system used in an airliner, and sidestick controllers."