Thanks to @Christian_Glass for the request!
Displaced thresholds are marked by white arrows leading up to the threshold, or start of the runway. They look like this: Most aren’t this long but the reason they are there is to protect incoming planes of obstacles on the glide path. Some airports do not have a displaced threshold and they aren’t marked properly in IF - if you see a long, blank area:
Displaced threshold can be used for takeoff if needed as it gives the runway extra length but it should be never used for landing. If you see a long displaced threshold, you still aim for the threshold markers at the start of the actual runway. This means you will not go lower due to the displaced threshold.
So, in Infinite flight, remember you should not land on the blank area. You may take off on it however. Always aim for the ‘piano tiles’.
Again, not all runways have this - the picture below has neither a blast pad or a displaced threshold.
Also note that if you are calculating runway distance, you still count the displaced threshold. If on the opposite end of the runway, you are permitted to use it as an extra roll out area.
Temporary displaced thresholds have the same rules but have slightly different markings. The image below is a temporary displaced threshold.
The runway also has a blast pad but the displaced threshold is considered temporary due to the chevrons before the official start of the runway.
Think you knew all that? Try this quiz I found: