FAR 61.1:

XC = Flight which involves landing at a point other than the departure airport.

XC for PPL/IR/CPL aeronautical experience = Flight which involves landing at a point other than the departure airport which is > 50NM straight-line from the point of departure.

XC for ATP aeronautical experience = Flight which is > 50NM straight-line from the point of departure (no landing required, this provision exists because military pilots usually RTB after a mission without landing anywhere else).

So...

- To log generic XC time, you need to land somewhere else.

- To use that time for PPL/IR/CPL you need to land > 50NM away.

- You can also log XC for the ATP rating without a landing if you fly >50NM from base. I would almost think you should log this separately from generic XC time since it can't be used for things like 135 requirements.

I think but am not 100% certain that the generic definition applies to 135 requirements also. Anyone?