Replace x with number in list within aircraft.cfg

[fltsim.x]
title=Boeing 747-400 PaintUPS
sim=Boeing747-400
model=
panel=
sound=
texture=UPS
kb_checklists=Boeing747-400_check
kb_reference=Boeing747-400_ref
atc_id=N747K
atc_airline=Boeing
atc_flight_number=1123
atc_heavy=1
atc_parking_types=CARGO
ui_manufacturer="Boeing"
ui_type="747-400"
ui_variation="United Parcel Service"
ui_typerole="Cargo Airliner"
ui_createdby="Microsoft Corporation"
description="World class delivery service"