I would definitely look at 1/144.
There's next to nothing in 1/48, and although 1/72 is a big scale (my fav) really doodly squat except for the very nice Heller DC-6 (my favorite kit ever, all subjects, all scales), and a couple of Boeing 377 models that aren't very accurate except for Pan Am. No United, BOAC or Northwestern. All the DC-3's are with cargo door and most modelers in that scale find vacs. The Heller Constellations are nice. Mach 2 makes a Caravelle that's great but it's a "basis" kit.
There was a great era in passenger aircraft kits in the early sixties. Lockheed Electra, 727, DC-9. alas no Vickers Viscount. But they were all box scale.
In 1/144 there's all kinds of kits. I recently built a DC-4 for Dad, who retired from United Airlines with 49 years seniority, Minicraft makes a lot of models at that scale that are all just peachy.
I have a few more in my stash, and we'll see because i do not like the scale.
In hindsight however Boyd, I think 1/144 is the way to go.
The big problem (more on that in a minute) is that your " favorite" subject in civil a/c is not available in any scale.
Curtis Condor is but it's 1/80.
Want a DC-10?
Heck, Concorde is completely under served by the early offerings and at this time there's one only.
Dad entered the engineering ranks at UAL in 1953 and was asked to figure out why United had lost two Stratocruisers in a year on the SFO HON route. One circled and ditched at the weather ship/ beacon that was mid way.
The big problem was that the R4360's had a lot of power but also created a lot of drag when they were at full throttle because of the cowling flaps being wide open and the big props at optimum pitch. So the flight engineer had to load them up to get optimum air speed and they would over heat. in both losses, the engine burned and dropped off the wing. At that point the flat area of the fire wall caused the a/c to pitch over and fight the pilot.
At the root of the problem was the conversion of priorities from route length to route speed.
When I first flew to Hawaii in 1959, and I was 4; there were two flights, following the railroad model.
The First Class flight took off from SFO at 9 am in a 377, and the Coach flight took off at 11.15 am in a DC-6. The two planes landed one right behind the other at Honolulu.
Go 1/144