Each time you send passenger planes out, you must choose a destination. Repeatedly collecting from the same route gives you mastery levels. Getting to 3 stars on a route will give you a reward item. Refer to the chart for route and reward information.
Neighbor's passenger planes can be sped up, by clicking on the orange cone when a plane that is currently on a trip, and you can collect from full planes. This started with a goal in That's the Ticket! You can also place Hearts on any plane or orange cone to ask for help.
According to Zynga's Board all planes may now be stored in the Warehouse.
Based on players' experience as posted in this thread, neighbors now can help with both passenger and cargo planes, they can speed them up and harvest them, counting towards mastery and un-withering is under investigation but comments say it counts towards mastery