I think you're confusing the quoted sentence and "I think airline tickets are expensive".
It is more likely that he is 'confusing' the quoted sentence and the findings from analysis of business failures (and marginal successes) in the industry in question compared with other industries and various analyses about the market forces that produce that result. This is still not quite the same thing as "commercial aviation is just barely economically viable today" but far closer than "I think airline tickets are expensive".
(I agree with Lumifer that Army's conclusion does not follow. Tripling the cost of fuel would still result in a viable albeit far, far smaller commercial aviation market.)
The cost of fuel seems to account for about 20% of the cost of the ticket on a US domestic flight (source). Given that international flights have higher fees, I expect the fuel cost percentage to be even smaller for them.
For example I took a look at a New York - London return economy ticket which costs about $1050 now. Out of that amount $250 are government taxes and fees (NOT including the sales tax).
Note: Please see this post of mine for more on the project, my sources, and potential sources for bias.
I have written a couple of blog posts on my understanding of climate forecasting, climate change, and the Anthropogenic Global Warming (AGW) hypothesis (here and here). I also laid down the sources I was using to inform myself here.
I think one question that a number of readers may have had is: given my lack of knowledge (and unwillingness to undertake extensive study) of the subject, why am I investigating it at all, rather than relying on the expert consensus, as documented by the IPCC that, even if we're not sure is correct, is still the best bet humanity has for getting things right? I intend to elaborate on the reasons for taking a closer look at the matter, while still refraining from making the study of atmospheric science a full-time goal, in a future post.
Right now, I'm curious to hear how you formed your views on climate change. In particular, I'm interested in answers to questions such as these (not necessarily answers to all of them, or even to only these questions).