When I studied linguistics, I took a seminar on text linguistics. In that seminar, we learned about paragraph markers. Written text is not always visually structured in accordance with linguistic paragraph markers, of course. Often readability and layout concerns have an equal weight. But lets push those aside for the moment and look at the linguistic markers only.
I don't remember all the markers, but the one I most prominently remember is this: Each paragraph has its own subject. At or close to the beginning this subject is introduced by name, and the following instances refer back to this first mention by pronoun:
Kuo ... himself ... He ... his ...
Following the signals of this type of paragraph marker, as soon as another subject is introduced by name, a new paragraph begins.
Mei-Ling is not a new subject in the first sentence, but an object of Kuo. Also, no new paragraph begins within a sentence, obviously.
But the airplane is a new subject, so here is the next paragraph:
a Boeing 747 ... its ... its ... A giant silver bird ...
"An gloomy orange." is a bit of a halfway sentence, as it stands. As a separate sentence it seems to introduce a new subject (the gloomy orange, which may refer to the outside view in general), but it does not make much sense as its own paragraph, because on its own it is strangely void of action and purpose. Also we can understand the "gloomy orange" to be a description of the sunlight pouring in in the previous sentence, so the gloomy orange is still on the inside and actually a part of the first paragraph. I would include it in the preceding sentence, which makes the whole construction more elegant and the meaning more clear: "Sunlight poured in through the window of the observation area, a gloomy orange."
The next subject, after the Boeing, seems to be Kuo again, because he is the first person named in the next sentence, and he is the first subject acting in relation to an object (turning towards Mei-Ling). But within the same sentence Kuo loses subject status as soon as Mei-Ling appears: she is the subject of everything following her name:
Kuo => Mei-Ling who ... she ... she ... her ... she ...
So in fact Kuo is not the subject here, he only serves as facilitator of a transition from him to her. He is a sort of conjunction, like the words "and", "but" and "meanwhile". You could do without Kuo in this last part, without losing any of your meaning (except that we would think of Kuo still looking outside, and the transition would seem somewhat aprupt).
There are other pragraph markers, such as words and phrases defining time and place, e.g. "beyond the glass" in your text. Along with the change of subject, the change of location signifies that with the Boeing a new paragraph begins. "Kuo turned back" has the same location shifting purpose, which supports my analysis that Kuo is not necessarily the subject here, but only serves to shift the narration to a different place and topic.
So, to put it all together, in my opinion the paragraph structure of that fragment is:
Once again Kuo found himself standing face to face with Mei-Ling at the airport. He looked to his side. Sunlight poured in through the window of the observation area, a gloomy orange.
Beyond the glass, a Boeing 747 parked in profile, its wings curving slightly upwards, its metallic surface mirroring the evening sky. A giant silver bird designed to help people fly to their dreams, to their journeys, to their new destinations.
Kuo turned back to Mei-Ling who was carrying medium-sized Boston bag and an Asus Laptop case. Unlike most girls, she liked to travel light; she hated carrying too many heavy things on her shoulders. It was something she wanted to avoid at all cost. Even for long trip like this one.
After we have considered linguistic paragraph makers, in the end we need to return to layout and readability concerns.
A one line paragraph will appear uncommon outside of direct speech and therefore emphasized. If you don't want that emphasis, just paste this sentence to the preceding paragraph, ideally with an appropriate concunction.
E.g. don't do:
Peter [very long paragraph].
John stood outside and smoked.
Peter [very long paragraph].
Peter [very long paragraph], while John stood outside and smoked.
Peter [next long paragraph]
Only if you want to emphasize that John is doing nothing while Pete works his ass off, do the first and give him a separate paragraph.
Paragraphs that span several pages will make your text hard to read, so break it even if the subject remains the same. The reverse holds true for very short paragraphs:
John took a card.
Pete took a card.
John took another card.
While this is certainly easy to read, apart from being bad style, this will look strangely chopped if it goes on for a few lines. Better put all these short sentences in one paragraph:
John took a card. Pete took a card. John took another card. Pete frowned. John smiled.
Linguistically these are all different paragraphs, and we do not want to connect the sentences with conjunctions ("John ..., and then Pete ..., while John ..."), because the abruptness of the transitions intensifies the competitiveness of the situation. Still, this feels like a completely fine paragraph, because, we might say, John and Pete are the subjects here, and their alternating ping-pong activity is the unifying action.
None of this applies to your example, I just want to add these considerations of readability, layout and semantics for the sake of completeness.