In case you did not know, X-plane offers two types of "time" compression.
I think it is Ctrl-T and Alt-T.
Ctrl-T increases computing speed and your computer need to be able to run the whole X-plane simulation at a faster rate.
Alt-T increases "ground speed" up to 16 times.
Both keys cycles through four "levels" of increase.
Some planes does not work well with these, and some only work at lower levels.