But aircraft weights etc, of the same aircraft type may be different.
If you just get some charts and a centimetre ruler, if an aircraft cruises at, let us say, 420 knots then it cruises at 7 nautical miles per minute. Airways charts have the point to point distances on, the rest can be calculated with the ruler and an appropriate 'add on' for taxi out, taxi in, climb and decent.
A computer cannot guess which SID or STAR will be allocated thus the old-fashioned way is just as good.