I didn't pull it out of thin air. The Lightning's picture is on page 183 of TR3057, in the Medium Fighter section, near its stat block (as with all the fighter images, aside from the Vulcan, which is on the very last page of the book). As TR3075, pg. 251, shows, Doug barely changed it.
Here's the complete list:
TR3057, pg. 179 / TR3075, pg. 212: Sabre (completely redesigned)
TR3057, pg. 181 / TR3075, pg. 231: Centurion (identical)
TR3057, pg. 183 / TR3075, pg. 251: Lightning (identical)
TR3057, pg. 185 / TR3075, pg. 189: Hellcat (identical)
TR3057, pg. 187 / TR3075, pg. 265: Eagle (identical)
TR3057, pg. 189 / TR3075, pg. 287: Thunderbird (identical)
TR3057, pg. 224 / TR3075, pg. 303: Vulcan (completely redesigned, thank God)
Keep in mind that AeroTech was originally going to use the fighter visuals from the Crusher Joe anime. Only one design carried that over, the SL-25 Samurai from Sorenson's Sabres, as pictured on the cover of the original AeroTech boxed set. When that plan fell through, either because 21st Century Imports couldn't supply enough model kits or because FASA started getting cold feet about using licensed images, all of the fighters were redesigned by David Deitrick. Go back and look through the old sourcebooks, and you'll see that every picture of a given fighter shows it from the exact same angle. For years, FASA treated Mr. Deitrick's drawings as clip art, barely modifying them from product to product. This wasn't uncommon, even with Duana Loose's 'Mechs, but it was especially pronounced with the aerospace fighters. I don't think Mr. Deitrick ever worked with FASA again, which also explains oddities like the Stuka miniature's weird, tiny cockpit. The artwork shows it from below, and without the original artist's feedback, the sculptor had to make his best guess.