This is the 8697th most frequent Russian word.
пассажирский
Passenger.
Here, 'пассажирский' is used as an adjective to describe the type of the train, indicating it is designed for carrying passengers.
Этот пассажирский поезд отправляется в Москву утром.
This passenger train departs to Moscow in the morning.
In this context, 'пассажирские' again functions as an adjective, here qualifying 'перевозки' (transportation), showing the involvement of passengers.
Летний сезон увеличивает спрос на пассажирские перевозки.
The summer season increases demand for passenger transportation.
The word 'пассажирские' is used attributively to describe airplanes, distinguishing them as ones designed for passengers.