Firstly, Nominus Prime was after Nova Prime as can be seen by the fact that Orion Pax and the nameless senator are talking together next to the Ark-1 memorial so it's safe to assume that Nominus was the Prime after Nova went missing (though I'm sketchy on how the Matrix didn't go with Nova on the voyage...). There's also Sentinel Prime to come yet before Optimus.
I reckon at this time that once the "true" Autobots start to form against the corrupt government that they might have chosen to stick with more ground-based alt-modes to differentiate themselves from the corrupt senators as much as possible. Most of the government senators have sleek, aerodynamic designs which alludes to aircraft alt-modes. As to Nominus being a jet, well, why not? That's what was "in" at the time.
*shrug* My two cents worth.
As to those asking whether this is G1 or not: no, it's not "G1". It's a different iteration of what we grew up with. It's not going to tie in with the cartoon or the 80s comic. This was a reboot of the franchise from the get-go and is taking ideas that existed before and reshaping them and giving us new stuff on top of that to boot.
Sorry, I don't mean to sound narky, I just get annoyed with people who go "OMG!!! That's not how it went in the [insert whichever iteration of TF you grew up with in the 80s and 90s here]!!!1! SACRILEGE!!!!1!!11!" Seriously? You just want a re-hashing of old material? Well, there's a plethora of it out there, go and reminisce to your heart's content.
Now, let me prepare for the flaming hot bile coming my way in......
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