About 287 nm — roughly 1h 02m in a midsize jet. 1 leg live on this route right now.
Every price on EmpTleg buys the entire aircraft, not a seat.
Sofia to Spata-Artemida is a different flight with its own aircraft, its own days and its own price: empty legs from Sofia to Spata-Artemida.
Nobody schedules an empty leg. One shows up here because an operator has an aircraft finishing a trip near Spata-Artemida and needs it near Sofia — or needs it home, and this direction happens to be the way home. That is why the flight can be a fraction of a full charter, why it can vanish within hours, and why the return direction is a different flight entirely with its own price and its own aircraft. Watching the route beats searching it once.