I wasn't sure about the ending to Jetman at first, but on reflection I think it largely seems right. Kaori was often shown to be like Rie, to the point where it felt pretty obvious that she would be her 'successor' (for lack of a better word). Even when she was with Gai it was obvious her heart really was still set on Ryu. She was shown to be saying (according to the GUIS subs) to Ako that she didn't think her relationship with Gai would last, and after that the "end game" of the series had her going after Ryu to save him rather than concerning herself with Gai, who she had already seemed to have drifted apart from. For me personally, Jetman is about the destructive side of love. Ryu spends the entire series trying to deal with it. Gai's unrequited love leads him to redeem himself, but ultimately that costs him everything. IMO the ending works well for those two character arcs. I wasn't sure about Gai's death at first, having heard it was just because they were copying the fate of his Gatchaman counterpart, but Gai's story isn't that of a traditional hero's, and Inoue shows that (perhaps more like real life) redemption doesn't mean you get the girl or even a meaningful death, and leaves it to the viewer to ask whether his redemption had worth in itself, whether it was it's own reward.
