Hi. This is an attempt to make the hiring process just as interesting and near as fun as getting your passengers to fly with your airline, and to turn it from something you have to do to something you want to do by introducing another dimension of play to the simulation. I'm no expert in aviation but I entertain this idea. Perhaps making the hiring process competitive between airlines, adding a set of factors that makes pilots want to fly for that airline just as there are for passengers, and I'm pretty sure salary isn't the only determining factor so a whole set of decisions would have to be made so it is dynamic, and tailored for that airline. Since this simulation is also a history game, the basis for all of this is a historical data of commercial pilot growth of the world or a country to create the pilot pool, if such data exists. The data can be visually represented in a graph or a pie for ease and for visual impact. If no data exists, perhaps interpolating a data based on air travel demand, population,etc or even any related numbers we have available in this version is a good start. All airlines will draw their pilots from this pool. And when pilots are fired, they go back to the same pool. Obviously, tweaks would have to be made so that no single airline will have most of the world's pilots but also keep it somewhat competitive so that there is no equal distribution and it is market driven. This will influence the rate at which an airline will grow over time.
Ground workers on the other hand, may be less inclined to relocate outside their own country where the base is doing the hiring and if it's a big country, then outside a region in that country. So a set of rules would have to be made for the worker pool so the pool is much more competitive between airlines based in the same country or a region in a large country than it is outside the boundaries.
This is just a general idea. Nothing is set on stone. The specifics can be worked out with what's real and what's technically possible. If there is someone who is an aviation expert or in depth knowledge on this, feel free to share.