When FSX is started, the default flight is also starting to load simultaneously in the background by default. It is designed to speed up the loading process subsequently.
However, if an FSX system has installed a lot of sceneries or the sceneries installed are large and demand a lot of resources (such as Orbx’s sceneries), it is very likely that one will encounter short hang-ups while changing airports and/or aircrafts or adjusting settings, due to the preloading process taken place in the background.
To get rid of this irritating short hang-up, one can include the following line in the [Main] section of fsx.CFG to suppress the preloading:
As mentioned, the short hang-up will only happen in a system with complicated sceneries or a lot of sceneries installed. In my nine flying zones, only the Australia and North America (with Orbx addons) and Europe and UK (with a lot of sceneries) regions require this tweak.