Passengers are one of the primary focuses of the airport. Passengers are the people who fly into and out of your airport, use your airport services, and are the main money earner for your airport.
Your airport is responsible for the handling of passengers onto planes, ensuring their safety through security and baggage screenings while at the same time managing their happiness. Passengers have a variety of needs, including happiness, bladder, tiredness, hunger, and fun. Each need can be fulfilled with different services that range from food, shops, bathrooms, and seating.
Departing passengers will arrive at your airport via transit options, and then sit down, eat if they want to, shop if they want to, and use the toilet. Then, when check-in opens they will check-in, and then immediately go through security. There, they will (if needed) shop, eat, sit, and use the bathroom. Lastly they will board the plane and leave.
Arriving Passengers will depart the aircraft, and if arrivals and departures are not separated, use secure amenities. Then they will reclaim baggage and leave the secure zone and eventually leave the airport via transport options. Or, they may leave the secure zone and then reclaim baggage.
Here is a diagram outlining the flow of passengers:
Happiness is affected by various factors such as Staff friendliness, wait times, and facility cleanliness. Happy passengers are more likely to spend money in your shops, bringing in more money. However, passengers that want to shop but can't will become unhappy.
Bladder problems in passengers can be relieved by constructing a bathroom.
Passengers being tired is a common problem that can be solved very easily, via seating. Ensuring seating to all passengers will make sure they do not get tired and not spend more money at your airport.
Passengers will eventually get hungry. Fulfill their needs by constructing Restaurants and vending machines.
Passengers at your airport will want to have some fun! You can fulfill this need by building a shop!