The game has an interesting feature for getting contracts with people you don’t know and probably never will be in contact with.
It can be a source of lot’s of contracts when your “regulars” are maxed or from airports less played by them. Or for getting contracts for B cat planes 
.
I have made it " standard procedure" to send some of my planes to nearby airports but without requesting a named player, so selecting No.
At the destination airport these planes are handled by players who are selecting “Random player arrival” with the contracts button.
When they do, their name is added to your list of “known” players for that airport. This list appears when you select “Yes” in the screen above.
At that moment you can offer a contract to that player which you know that they are actually at that airport.
There are some drawbacks. You are not sure that your contract is accepted and during the wait it takes up a stand/gate. Also, the reliability of the player is “unknown”, with your planes reappearing after considerable delays.
Happy flying.
