Is there a reason you don't want to leave the top clear? I'd just paint it underneath and then put a clear coat of gloss over the top. Of course you'd have to put the Pan-Am logo on before you paint though. 

I dunno.  It just struck me the wrong way immediately for some reason.  Seemed like it would look "funny" with the outlines being extra thick plastic.  Seems like that would still show through even when painted.  I'll take another look at it though with fresh eyes.

Hmm, maybe you could find a good image on the internet and print it out, paste it over the logo and then clear coat?

No idea if it would look good or not, just throwing out ideas... 

Sounds like an ideal job for Tamiya Clear Blue.

I might be tempted to spray inside and out, then sand the inner raised surfaces to "clear" again.  Or not, I'm of two minds on that.

Another option would be the Tamiya Clear Smoke, shot only on the inside perhaps.

From my experience painting RC car shells, I'd say just paint it from the underside. It gives more protection from chipping as the paint is on the inside, you don't need to use a gloss coat. If you do it though, you need to think backwards when painting, ie. Start with lattitude/longitude lines, land and then water.