While probably of little interest to the average person, here’s something I find to be interesting regarding how airlines choose to brand themselves.
In this post:
Airline, airlines, air lines, and more…
Airlines brand themselves in different ways, and I find that distinction to be noteworthy, especially given how often airlines are referred to incorrectly in the media. For example, you have American Airlines, Delta Air Lines, and Emirates Airline. There are options beyond that as well, as you have companies like Qatar Airways.
I know these distinctions might sound minor, but you’d never guess how much it irks people at some airlines when you get these things wrong. For example, if you apply for a job at Delta and refer to the airline as “Delta Airlines,” your odds of landing a job offer will go down drastically. Sure, that might seem silly, but in fairness, I suppose it’s a basic test to see how detail oriented people are.

Is one term more logical than the others?
Private companies can market themselves however they’d like to. But is there one form that’s more correct, between airline, airlines, and air lines? I’ll share my take, but y’all are welcome to correct me and chime in.
Looking at dictionary definitions, it seems like an airline is defined as “an organization providing a regular public service of air transportation on one or more routes.”
So if you’re using a strict definition like that, I’d say Emirates has it right, referring to itself as Emirates Airline. It’s one organization providing regular public air service on one or more routes.
But this is also a bit more nuanced. For example, most of the major US carriers are actually combinations of many smaller airlines through mergers over the years, so it’s not unreasonable that they would add an “s.” For that matter, many airlines have wholly owned subsidiaries, so I suppose there are multiple organizations providing transportation under the larger airline branding umbrella.
And I get the Delta Air Lines branding as well. An “air line” can also be defined as a single route or connection between two points, and Delta provides many different “air lines.”
So yeah, the moral of the story is that airline, airlines, and air lines, are all correct, it’s just a function of how you want to look at it, and how a company wants to market itself. But if you’re applying for a job at one of these companies, be sure you get that detail right.

Bottom line
It’s not something a non-aviation geek will typically put much thought into, but not all airlines market themselves the same. Even taking “airways” out of the equation,” you have “airline,” “airlines,” and “air lines.”
There’s a logical explanation for each of these. I think “airline” is the most traditionally correct, in terms of one organization providing many routes. But the other two work as well, it’s just about how you frame it.
Where do you stand on airline vs. airlines vs. air lines?
Last year a friend of mine, (pilot), was having their Delta application reviewed by an interview prep service. His resume had “Airline” on it, he was told he needed to change it to Air Line for his application to be considered. Funny how different each company is.