It turns out Boeing 747 can carry an extra engine under its left wing in case there's need to transport an engine somewhere far away. The engine is attached between the body and the left inner engine and isn't operational during such flight.
What implications does that have on the airplane operation? I guess drag is increased notably and also drag increases only for left wing and so the plane should tend to well, turn left in case engine thrust is equal on both sides of the plane so now engines under right wing have to produce more thrust or something like that. Also the engine weighs quite a lot so less cargo may be put into the plane. Also fuel consumption increases and flight range decreases accordingly.
Is that all? What are the consequences of attaching an extra engine under Boeing 747 wing?