I'm not sure they're even used for that purpose - that side of thing is done "live" as I understand it - the plans are so that ATC has the details on hand for e

I'm not sure they're even used for that purpose - that side of thing is done "live" as I understand it - the plans are so that ATC has the details on hand for each flight and it doesn't all need to be communicated by radio as they pass through.