When I was much younger I was given a copy of the DS9 Technical Manual. I poured over the schematics of DS9, but I especially remember the pages at the back of the back with technical data and drawings of Starfleet vessels. Amongst those was the Akira Class. I don’t recall ever seeing one in any episode or movie, but according to the issue 12 magazine the USS Thunderchild did appear in ST:First Contact.
Of all the Starfleet vessels I have received this is my favourite design. It’s very similar to the Enterprise NX-01, the two seemingly built upside down to each other. Compare these two images of the NX-01, top side up and the Thunderchild, upside down.
The basic hull layout is the same, aside from being upside down from each other. The Thunderchild has a considerably more ‘modern’ style nacelle, a larger secondary hull between the nacelle struts and massive lengthways struts joining up with nacelle struts. These are large enough to be decorated with four rows of windows, implying they are at least four decks tall.
The ship is very well detailed, though as I don’t know it very well I can’t vouch for it’s accuracy. There is no aztecing, but plenty of embossed hull plating, windows and transparent parts. It’s one of the few ST:TNG era models to have a separate deflector dish piece made of transparent blue.