I don’t see the advantage of using the builder pattern in the aircraft example.
A f16 cannot exist without an engine, so the director always has to create an engine, what’s the benefit over the factory pattern? Also, the f16 builder should know that it doesn’t have a bathroom so it doesn’t need a director to take over this decision.
Besides that, not using methods of an interface violates SOLID’s interface segregation principle (letter I).
I feel like it only makes sense to use the builder pattern if there are optional steps, e.g. like in the document example where you might not want to set an author.