We reduce code coupling by ensuring the relationship between Passenger and FlightSeat is unidirectional (the directed chain of relationships are BookingSystem->Passenger->FlightSeat and BookingSystem->Flight->FlightSeat).
Law of Demeter is satisfied through the use of method forwarding.
Liskov Substitution Principle is not applicable, because there are no subclasses. No specific design patterns were used in this implementation.
It is important to note that inheritance and OOP patterns were not necessary in this implementation to represent different classes of seat (first class, business class, economy) because there is no special behaviour differentiating these seats. A more complex problem may require this – for example, if the problem was extended to include the requirement for different promotional deals on seats (such as 2 for 1 business class tickets, buy 2 get 1 free economy seats), we would need to use inheritance to model the subtypes of FlightSeat, and apply a visitor pattern to implement the promotional deals.