Hi, I operate an airline of 737, 757, and Canadair Regional Jets out of IAH. 2 of the aircraft types I operate in the 737 and CRJ have direct competitors (737-700 and a319 and A220, 737-800/737-900 and a320, 737-900ER and a321, CRJ-200 and ERJ-145, CRJ-700 and E170, CRJ-900 and E175, CRJ-1000 and E190) I was just curious on your opinions on which aircraft families are more profitable in different situations such as short, medium and long range. Along with different aircraft types such as 787 vs A350, ATRs vs Dash 8s and Y-7s, a320neo family vs 737MAX family, etc. I know that there is the aircraft type evaluation tool but I have found that it doesn’t take all variables into consideration.
My 2 cents: The most profitable plane is the full one
I usually look at the market and lease what’s available
Optimizing capital cost is good for profitability and if you find good offers in the market you can reduce it (for example in some markets there are almost new A320neo for 200k/week and no 737MAX)
As noted in the first reply - the most profitable is the full one 
That being said there is no ‘perfect’ answer here. The best fit is the aircraft that provides you the most usability - the reason that the 737 and A320 series are so popular is that there are multiple versions sizes and types that can fit many different routes and ranges.
The regional jets provide you with decent short haul options. Or on a medium route with low traffic volumes. They are or can be incredibly useful.
Cheers
Indeed there IS some difference between the planes.
First of all and more importantly, you should check what kind of routes are you wanting to operate and if the plane matches all the restrictions and limitations needed. Therefore, you have to look on how many seats you can carry in configuration X or Y depending on what plane you have. Even further, one of the things you learn through time is that even though old airplane at the market are the cheapest ones to acquire and maintain, they have really expensive maintenance costs so probably you will need higher ticket prices in order to stay profitable.
Newer planes are more expensive to buy and to maintain weekly, but they have really low costs in general, so you can have a wider profit margin and operate better in places you might have competition and stuff.
And, as a last Personal note, deciding which plane you’re going to have is of personal taste because planes in similar category has the same numbers difference will be runway and range performances only.
But also, keep in mind that diversifying the crew too much also is something costly.
As a last point, there is a tool in-game for you to use there is really useful to compare the minor details - Aircraft Type Evaluation. Helps a lot even to calculate weight restrictions.
You contradict yourself with what you write
No, I don’t and it’s really simple to explain.
Lets get to numbers:
I have in my fleet a mix of the 737 classic (my workhorses), 737NG, Embraers and Airbus A220 for the regional and most of the national network. Most of the 737CL are -500s and also those are the oldest guys.
Let’s compare the A220-300 (my newest model) and the 737-500 (most used) of my fleet:
A220-300
Cost: 2.3 millions to lease plus 230k per week payment.
Seatings: 115 Leisure Plus Y / 15 Recliner Shorthaul C
Age: Brand new
Boeing 737-500
Cost: 315k to lease and 31k per week (average price due to severe competition to bid those lads!)
Seating: 102 Leisure Plus Y / 12 Recliner Shorthaul C
Age: Average of 26.1 years.
Now let’s show how these numbers work on flights:
I have a city pair (GIG-CGH) that is operated by both planes and have full flights with both. Is one of my most crowded and feeder routes, even though being only 45 mins and same ticket price.
The total costs per flight of PP-BCH (A223): 13.543A$
The same for PP-AFS (B735): 16.615A$
Now let’s see the ticket income:
PP-AFS: 12.588A$
PP-BCH: 13.830A$
So, I have profit with the A220 and loss with the 735 on this single flight.
The 3100 A$ difference per flight is mainly due to maintenance, since AFS is a 30y old plane.
That’s what i’m talking about. If i want to have profit with the 735 on that specific flight, I will need to raise ticket prices but I can’t due to a strong competition and already a LOT of flights, meanwhile I still can have some profit with what I have on the A220 with a gap in between them of almost 5k A$.
To buy the A220 you spend almost 2 million more per plane and have to pay ten times more almost per week than the old 735. But the outcome of this enterprise can be good, as I just showed ya.
Do I have routes that I have profit on 30y old planes? I do! Plenty! But, mainly, are routes with less competition or a demand so high that high ticket prices can be used and still guarantee a plane filled up, just like what I do with my A300s/MD-11s on higher demand national flights.
And there is where you have to think what will be best for you.
I opted to start with the 737CL because of the quantity of planes you can have with a small amount of money and make actual money with them spending less, but newer planes can generate a whole lotta more revenue and you have to put that on a balance and play your game.
Hope that this gave some insight.
No you don’t understand at all.
I am not talking about old vs new.
You write:
1.
Old is cheap to maintain but have expensive maintenance. First contradiction. How can a cheap to maintain thing have expensive maintenance?
New is expensive to maintain but has lowncost maintenance. Second contradiction. How can an expensive to maintain thing have cheap maintenance?
As far as your economical comparison of new vs old, you are preaching to the choir .
My comment all comes down to your used language contradiction, not economical contradiction of new vs old.