Originally Posted by Indelaware

One can never know for certain if a particular aircraft will be used for both A>B and B<A, even at a small airport with one scheduled flight. Does the airline have an extra aircraft on-the-ground (perhaps from a previously cancelled flight or other IRROPS)? Does the airline do MX at the destination station, either themselves or through a contractor? If so, then the airline may swap aircraft at that station every day. Even when the same aircraft is planned for A>B>A it is always possible that B>A will cancel.