Now, I'm just using my general knowledge and Wikipedia and aviastar (if I had Jane's all the world's aircraft, that's what I'd use as that's what they use for most of the aircraft), since I've never had the privilege to start so early yet.
I hope you don't mind an overview from what I see for the next 5 years.
According the Aviastar, the Ford Trimotor, has a capacity of 17 (though Wikipedia lists 10, so I suppose that 17 is more or less a paratrooper config), a max. speed of 130 kts (wikipedia shows 78 kts as a cruising speed, so I'm not sure which piece of data they'd follow here.) It's max range falls short shows up as 478nm. It becomes available in 1925. So if that is correct, then that should be the first plane with more than 14 passengers. So from what I see, if the max speed and that larger capacity is used, then you have 2 of the 3 combined.
Next aircraft that may come to intrest to you in terms of passenger capacity is the Armstrong Whitworth Argosy. According to Aviastar and Wikipedia, it has capacity of 20 passengers. Unfortunately, from what I see, it suffers from low range (352 nautical mile range) and low speed (max 96 kts, cruising 78). So from what I see, only 1 out of 3 here.
Next Plane, also introduced in 1926 is the Belriot 165. This aircraft has accommodations for 16 passengers. The max. speed is under what you are looking for (100 kts), and the range is less than the Argosy's at 283 nautical miles.
In 1929, you should look forward to the Boeing Model 80, it has a max capacity (according to aviastar) of 18 passengers (though it did also mention in the history 12, not sure what the game will follow), a fairly attractive speed for what you're looking for (108 cruising, 120 max), Though on the range, it does fall short for what you are looking for in longer range (400 nm).
Also in 1929, you'll possibly have a VERY GOOD year on the capacity front! The Fokker F32 is introduced, and it can carry 32 passengers, it has a cruising speed of 102 knots and a max speed of 134 knots. It also has a fairly attractive range of 643 nautical miles! Something I think you should watch for. I don't know the stats the game will use, so check in the game in 1928.
Next in 1930 is the Junkers G.38, capacity from what I read here 34, range 540 nautical miles, cruising speed of around 113 with a max. speed of 121.
From what I see, your first chance to get an aircraft with all 3 characteristics is the Douglas DC-3! It lists on Aivastar as 21-28 passengers, with a range of 1304 nautical miles, and a cruise speed of 158 knots! I think though that the game may list the range lower, but from what I remember using these in a late 1940s/early 1950s round, that speed and capacity should be correct. It is introduced in 1935, and from what I see, the mid-1930s will possibly the be era you may need to look out for! Right now, you're in the era when the concept of the airline is still in it's infancy and hasn't exactly gotten all that far yet and aerodynamic design was just starting to be understood better. Ideas like flutter were not understood yet, and lead to some impressive failures, such as the Kalinin K-7 from the early 1930s (which isn't in the game, but from what I read, if used in a civilian layout, could seat up to 120 passengers.)
