If a pilot is only type-rated to fly an Airbus 320 he is not allowed to even try to fly an 737 nor a different type of Airbus. This attitude of "a car is a car,

If a pilot is only type-rated to fly an Airbus 320 he is not allowed to even try to fly an 737 nor a different type of Airbus. This attitude of "a car is a car, what can go wrong?" is deadly in some domains.