What determines what panel instruments are fitted into the cockpit of Airlines?


When looking for example at an A321-232, some of the panel instruments are different despite it being the same variant, sometimes even if it the same airline company. So my question is straight forward: What is the underlying factor that determines what panels are going to be fitted into the cockpit, if it isn’t determined by the variant or airline?

In: Other

Aircraft manufacturers have “standard packages” and individual airlines sometimes want optional extras. [(ref)](http://www.smartcockpit.com/docs/A320_Flight_Deck_and_Systems_Briefing_For_Pilots.pdf )

That said, the six display units(DU) are interchangeable, switchable by the pilots, and integrated into the same system architecture (EFIS / ECAM). What you see on them largely depends on what the pilots were last looking at.