Hi Ian,

To add a new call sign to the default list of aircraft call signs, go to: Computer > Local Disc > Program files (x86) > Microsoft games > Microsoft flfight simulator X > airlines.cfg , and add the new one.

Beyond that, be sure to change the old call sign, at: Computer > Local Disc > Program files (x86) > Microsoft games > Microsoft flfight simulator X > SimObjects > Airplanes > [Airplane model] > aircraft.cfg , e.g., as shown below:

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[fltsim.2]
title=Boeing 737-800 Paint4
sim=Boeing737-800
model=
panel=
sound=
texture=4
kb_checklists=Boeing737-800_check
kb_reference=Boeing737-800_ref
atc_id=N737T
atc_airline= -----> (add new call sign here)
atc_flight_number=
ui_manufacturer="Boeing"
ui_type="737-800"
ui_variation="Orbit Airlines"
ui_typerole="Commercial Airliner"
ui_createdby="Microsoft Corporation"
description="One should hardly be surprised that the world's most prolific manufacturer of commercial aircraft is also the producer of the world's most popular jetliner. The 737 became the best-selling commercial jetliner worldwide when orders for it hit 1,831 in June 1987 (surpassing Boeing's own 727 as the previous champ). However, it wasn't always that way\s in the first few years of production, there were so few orders that Boeing considered canceling the program. They didn't, and the airplane has more than proven itself in over three decades of service."

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Remarks:

1) If you are a W7 user, open the files "AS ADMINISTRATOR", or you will not be able to save the changes.

2) I don't know the reason, but sometimes FS system doesn't accept the changes you did.

Hope this helps.

Pinatubo.