Airline Club

I would like to see the big alliances broken up to create more competition.  The biggest alliances can attract the biggest airlines and create an entrenched position at the top with more bases and bigger allies than any challengers.  If alliances were capped at 6, there would be more of them competing with each other, and each alliance would have less advantage over upstarts.

There are many airports that are too small to matter.  They clutter up the map and waste time when searching for new routes.  Maybe eliminate everything under 30-50k unless there's a specific reason to keep it.  I would rather see a few more airports in the 50-200k range if needed for starting players.

I know this has been mention before, but I would like to mention that Boston (BOS), Seattle (SEA), and Miami (MIA) in particular have strategic locations and could be several times larger.  As others have suggested, county data is useful for looking at US cities.  Miami-Dade county is 2.5M compared to 0.5M for MIA airport (2010 data).  The counties containing Seattle and Tacoma create a similar picture for SEA.  Boston is a special case, and is broken up into different cities even though they are essentially one (Cambridge, Brookline, Somerville, Medford, Lynn, and Quincy are all very close to BOS airport, like within 20km).  I think adding a fictitious city such as "Miami Vicinity" would be an acceptable solution, or I would be willing to dig up real world data for cities such as the ones listed for Boston.

I will include an example from the game.  Right now I could borrow $100,000 for one year at $2,277 for 52 weeks.  This would be $18,400 in total interest and a total repayment of $118,400.  This is all good so far.  The problem is that the game calls this an 18.4% "interest rate."  In fact, the interest rate on this loan is much higher than 18.4% because the principle is being paid off over time, but the amount of interest charged doesn't go down.  I would be paying interest on money I have already paid back.  I tried to match the terms of this loan using the loan calculator and it is actually 34% APR.  Look at the top option, "Amortized Loan", at the link.  https://www.calculator.net/loan-calculator.html?cloanamount=100000&cloanterm=1&cloantermmonth=0&cinterestrate=34&ccompound=weekly&cpayback=weekly&x=70&y=22#amortized-result

On the other hand the 5 year loan overestimates interest rates for reasons I explained above.  I can also borrow $100,000 for five years at $487 for 260 weeks.  The game calls this 26.% interest, but it actually works out to be about 9.8% interest.  Again see the link and look at the top loan option "Amortized Loan."  https://www.calculator.net/loan-calculator.html?cloanamount=100000&cloanterm=5&cloantermmonth=0&cinterestrate=9.8&ccompound=weekly&cpayback=weekly&x=34&y=18#amortized-result

Conclusion:
1yr loan = 34% APR
5yr loan = 9.8% APR
The rates listed in-game are misleading.  It's not that big of a deal because the actual repayment amounts are accurate.  I love this game, and I only hope to be helpful. 

The key point is that the interest is charged each year regardless of the length of the loan.  Let's take a very simple example using "simple interest" instead of compound interest.  A $100 loan for one year at 10% interest would = $110 total repayment as you said, but a $100 loan at 10% interest for 5 years would = $150 because there is 10% interest each year. 

The situation you describe with the 5 year loan does not reflect the circumstances because the borrower gets the full $100 at the beginning and gets to use the $100 for five years (less the amount repaid over time which does reduce the interest). 

Maybe think of the 5 year loan as a series of one year loans.  Suppose on Jan. 1 of 2010, I borrow $100 to buy an airplane part.  On Jan. 1, 2011, I owe $110, but I'm not ready to repay, so I pay $10 interest, but I borrow another $100 to repay the first loan.  The first loan is done, but on Jan 1, 2012 I owe $110 for the second loan.  Again I get a new loan to repay the old one.  Each year I have to pay $10 for the use of the $100 I continue to have borrowed.  A five year loan just combines this process.  (Actually it gets more complicated depending on the repayment schedule and compounding interest.)

Try playing around with a loan calculator such as this one: https://www.calculator.net/loan-calculator.html
You are using the first option: Amortized Loan, where the principle is paid off gradually over the life of the loan.  As an example I looked at a $100,000 loan for 260 months in game.  The total repayment was $124,100 (which the game calls 24.1% interest rate, actually its the total interest)  I played around with the interest rate until I got the same total repayment and it was 8.85%

A very simple solution would be to just eliminate the shorter loans (they are a terrible deal compared to the 5yr), and change the "interest rate" label to "total interest percentage" as I suggested.  The actual 5 yr loan rate seems pretty reasonable. 

I am a new player, but based on the stats, I would say the A318 is far too expensive for the number of seats, and it has way more range than you need for most domestic routes.  The Boeing 737-100 is very cheap by comparison and has almost as many seats, though it burns more fuel.  The 737-700C or Bombardier CS100 would be a good replacement if you need  long range and good fuel economy.  If you want a bigger plane, consider the MD-81 or the A20.  In real life I think 737s and A20s are very popular, but I don't know what is best in the game.