I'm pretty sure 'no' translates into 'the'>>>'of'>'in the'.
First of all, it really doesn't. の (no) is used anytime in Japanese to show the relationship between nouns or noun phrases where the first element modifies the second. For instance, 日本語の辞書 (nihongo no jisho) means "Japanese dictionary". "Nihongo" means Japanese and "jisho" means dictionary, but in this case the "no" doesn't really translate to anything in English. It can also be used to indicate possession the way we use 's in English but that's not relevant here.
So 空の軌跡 (sora no kiseki) could just as easily been translated to "Sky Trails". In fact I would argue that would actually have been a more standard, straightforward translation. Xseed went with "Trails in the Sky" because it sounds nice. And it does sound nice. It's got a nice ring to it. But "in the" is not
a standard translation of の. In fact it really only works in particular cases...like, Japanese doesn't even have articles so the choice of "the" instead of "a" is completely based on context. There's only one sky so "the" works in that case, but what about "Trails in the Flash"? What flash? What does that even mean. Why go with "in the" at all when it doesn't have that ring to it?
For better or worse, "Trails of Zero" and "Trails of Blue" seem to have caught on for Zero no Kiseki and Ao no Kiseki. In fact Udon even adopted those names for their English translations of some art books. I would still argue that they're pretty nonsensical names, though. I mean, "of zero" or "of blue" don't even sound grammatically correct. I'm really curious that if 20 years from now when Xseed finally gets around to doing those games if they're actually going to use those names.
But things get even more complicated when you get to 閃の軌跡 (Sen no Kiseki). In addition to the somewhat ambiguous grammar, technically 閃 (sen) isn't even a word. It's a character that appears in certain compounds with the pronunciation "sen", but it doesn't ever appear alone. It also has a verb form but it's actually pronounced "hirameku" there. Though kanji characters generally have meanings associated with them they're more ambiguous than dictionary words. 閃 can mean flash, but it can also mean brandish or even insight (as in a flash of insight I guess) in certain contexts. There are a lot of different ways that title could probably be translated. Not only does "Trails in the Flash" lack any of that nuance, it sounds fucking ridiculous.
But anyway, what's wrong with just calling it Sen no Kiseki? It has not been translated yet and until there's an official English title I'm just going to stick with the Japanese. But I will bet good money that if it ever does get translated, "Trails in the Flash" is not the name they're going to go with...