This might have been suggested before; sorry if it has been. Anyway, there is a pilot shortage that the real world airlines are facing right now. Pilot recruiting and retention can make or break an airline. I think I might have some ideas to (at least somewhat) introduce this to the game.
Pilot Flying Hour Requirement:
The airline can choose what is required to be employed at their respective airline. I think a drop down box/radio button option would work: 250 hours, 1500 hours, 5000 hours, 10,000 hours. Make it so 40% of pilots are in the 250 hour mark, 30% of pilots are in the 1500 hour mark, 20% of pilots are in the 5000 hour pool, and 10% of pilots are in the 10,000 hour pool. Now these "hour requirements" are just minimums to be employed at the airline, so an airline with a 250 hour requirement could hire a 10,000 hour pilot. The different pilot skill levels will bring in additional features, which will be discussed below. But first and foremost, let me state that You do not know how experienced the pilot is when you hire him. You don't get to see how many pilots are in each pool; just two values: A pilot pool (how many pilots in the country/world there are total), and An Applicant pool: How many pilots have "applied" to fly for your airline.
Pilot Pay
First of all, most pilots in the real world are unionized. So therefore, I think our pilots should have a "contract".. i.e., once you set a pay rate for your pilots, you cannot adjust it for two weeks, unless you add a different aircraft type. Then you can adjust the pay for just that new aircraft type. Pilot pay can do two things. First of all, impact staff mood (like it does already). Secondly, it can also dictate how many pilots you have in your "applicant pool". An entry level pilot with 250 hours can expect to make entry level wages, and would therefore expect to make less money. The pilots with 10,000 hours would want to make a ton of money. I think this should be a random percentage of the national average salary for each pilot tier in order to attract the respective tier. So (for example) If you pay... 50% of average salary, you attract 250 hour pilots. 100% of the average salary (so.... the average salary), you attract 1500 hour pilots. If you pay 150% of national average, you attract 5000 hour pilots. If you pay 200% (so double the average salary), you attract 10,000 hour pilots. Again, this would be random and not known to the community or the individual airlines. Now in the real world, you get 250 hour pilots who think they're entitled to 7 figures a year, and you have some 10,000 hour pilots who got 10,000 hours just because they love to fly. So I think this should include a random "fudge" factor from each pilot group. High time pilots who will work below the wage requirements mentioned before, and low time pilots who will work above the wage requirements mentioned before. This would require airlines to play with their salaries to see what happens to their applicant pool.
Fleet Size/Type/Age:
Pilots want to fly the biggest, newest, fastest, and best. Your fleet should have some impact on your applicant pool. I'd say the popularity with passengers should coincide with the popularity with the pilots. Also, if you add/subtract any aircraft to your fleet, that could be a sign of growth or shrinkage that can influence morale by a certain factor.
So.... what does this all mean?
Low Time vs High Time Pilots:
Why would someone want to market to low or high time pilots? Well, like I said, you have fleet and pay implications for each "tier". But I think low time vs high time pilots should also contribute to the image and reliability of your airline. If you have an airline full of newbies, you might incur delays and cancellations because they did something wrong. Highly experienced pilots know what they're doing, so less cancellations or delays will occur. Also, highly experienced pilots know how to find smooth air when encountering turbulence, so our passengers can have a smooth ride, therefore increasing image. Obviously the turbulence situation is hypothetical, but that's how high time vs low times can influence your image.
Pilot Retention:
Lastly, if your pilot mood gets below a certain threshold for whatever reason, I think they should start quitting. Conversely, if you have high morale, pilots might start telling their "friends", and you might start see your applicant pool creep up.
This might make things interesting. Again, sorry if it's been suggested before. Let me know what you think!