If you buy a car, you go to the dealer to pick it up.  If you buy an airliner, there might not be a dealer but you will still go to pick it up.  After the production test flights have been completed, the customer gets to carry out their own test flights.  If all squawks have been dealt with, time to pay and take the “keys”.  Then a crew from the airline will fly the plane to their home base.  This 787 had been handed over to LOT and the crew were flying it back to Warsaw.  Delivery flights are often obvious from the takeoff roll.  Fueled up for a long trip, they use a bit more of the runway than the test flights do.  In a short while, this jet will be busy plying the LOT route structure.