The Kangaroo is a small propeller plane unlocked at level 7 that has 4 cargo/passenger slots. This is going to be your Class 1 workhorse - it is the cheapest regular plane (16 File:Bux.png for a capacity of 4), has a decent range and can thus be very profitable. The Kangaroo will remain useful for events and feeder airports even when you are mostly relying on Class 2/3 planes later in the game.