The very first flight they were on together was spent in a subdued quiet—something heavy hung in the air between them, as they traveled to Australia, and it wasn't addressed during the flight. (It was only after they’d landed that Rin had apologized, and the air surrounding them lightened considerably.)
What few words were shared were largely spent over meaningless nothings to fill the space, to bridge the gaps of “What would you like to drink?” and “Do you want headphones? Here,” and easily forgotten by Haruka when he looked back at that particular trip (though part of it could also have been his own presence of mind, at the time).
Through it all, though, Haruka was able to see how Rin had come prepared, with an extra pillow that goes around the neck, perfect for sleeping while in an upright position, and his own eye mask and earphones. He supposed that Rin must have learned from experience, having taken these flights from Japan to Australia and back for years.
He’d heard enough from his parents about flying on airplanes, honestly, since they used to come back with different stories about their travels for him to hear, if he wasn’t able to come because of school or whatever reason. His parents had taken him to Taiwan before, though—he was just too young to remember much about the plane trip, besides it being his first one. They, too, were experienced with flights, which was partially why Haruka was able to appreciate just how knowledgeable Rin was (on the flight back, when he was in a better state of mind again).
Rin falls asleep quite easily (like Makoto), and always meticulously calculates the best time for him to fall asleep, apparently able to control when to sleep and when to wake up, thanks to his years of morning training; Haruka, on the other hand, could only fall asleep when he’d gotten comfortable enough, and even then was likely not to have the most restful sleep on a plane. (The best times were the ones where he woke up pressed into Rin’s shoulder, though, even if Rin’s muscles were hardly a soft cushion for his head.)
It was over a particularly long flight that Haruka got to watch Rin watch movies; Rin, engrossed in the film that Haruka couldn’t even hear, didn’t see the way Haruka had studied his face and how he reacted to different parts of the film. Haruka, on his part, was intrigued by just how many nuances there were in Rin’s facial expressions, making mental notes for later. (Rin was a sucker for romances, but he wouldn’t watch them on the plane until after he knew Haruka knew he liked them. He got Haruka to watch a film with him, on a flight to Rome, though Haruka didn’t really get what was so appealing about the “romances” he saw, but at least he knew what had Rin screwing up his face in sympathy, or frustration, or happiness.)
They would bicker over the food on plane flights, or really, the food choices they make, because Haruka would always get fish, mackerel if he was lucky, while Rin tried to get Haruka to try a “wider variety” of food; Haruka insisted that they could eat different food when they landed, which happened anyway with Rin, but Rin would insist that Haru had too much fish and needed to eat other things too, he’s had fish on every single flight, and Haruka would shoot back that Rin was exaggerating, some flights didn’t even have fish, and Rin would roll his eyes, but start eating before the food got cold. (It didn’t stop Rin from giving Haruka some of his meat, while taking bits of his fish, anyway.)
There was another flight where, while Rin was asleep, Haruka had extricated one of Rin’s earbuds to see what kind of music he listened to while he slept. Most of his songs were in English, and Haruka didn’t know what they were saying, but the songs sounded pretty nice, not too loud, and not too slow—surprisingly, since Haruka would have thought that slow ballads would be better to fall asleep to. (On a later flight, Rin shared his music with Haruka, and told him what the songs were about, too.)
Rin always loved to look out the window when he could, but would always make Haruka sit in the window seat, so he could make sure Haruka was looking, too. (He also probably liked leaning into Haruka’s space, or so Haruka had thought privately, but he’d never asked Rin if that was the case.)
(He didn’t have to.)