Maybe I'm not the right person to comment but I dont think TV ads will do much unless you have lots on money to flood the airwaves with multiple commercials,sort of like those free to play games..... 
I watch a fair amount of TV,but I seldom see commercials as I record/PVR most the shows and skip the ads whenever possible. I also watch several commercial free or low ad content channels simply because I hate being interupted with some TV ad.
I dont think I'm that far from what most do so TV ads IMHO are not the best value these days. 10 or 15 years ago I would have been on the bandwagon with pushing for TV ads but not so much today.
Social media,whatever that is, seems to be the wave of the future,a rat farts in india and it's all over the net,complete with video and commentary.
I like to wear my AH Tshirt when I go out were there's going to be a crowd and often people stop me and ask what my shirt all about. I think a buddy pass type system plus a free trial would do wonders.
Players could convince a friend to try the game then tell them if they like it all they need do is sign up for the 2 week free trial,which IMHO should be increased to a month or 30 days whichever comes first.
Then the rest lays at the feet of the players,if you are helpfull and treat others the way you would want to be treated we just might see those 5 to 600 player nights again!
As usual YMMV.

I think a few years ago now, HTC advertised AH on the History Channel, or something like that, using a promo video called "Fly Aces High". I'm sure they kept track of the results of that marketing campaign, and know $ cost per new player. I think it did result in an influx of new players, but only HTC knows what the ROI was.
Maybe an inexpensive way to increase numbers is gamer-to-gamer word-of-mouth. They could implement something like WT does, except as a clipboard MOTD popup, maybe once a month - the first time a player logs in after his month-a-versary:

I wonder also if it would be cost effective to print a bunch of CDs and put them in cardboard envelopes, and send a few dozen to every WWII aviation museum around the country, for free give-away in the museum's book shop.

And I've always thought it would be great for AH to have an organized presence at air shows. Build a few demo cockpits and hook them up in a tent, let air show attendees fly the planes online to see what its all about and give them a free game CD when they leave.
Last thing I can thing of that might help is a real cinematic presence on YouTube. And I don't mean filming your flights and setting it to a soundtrack of rock music, I mean planned short films and movies like Dolby, LePape2 and NirosAH2 did. "Hunt or Prey" and "Fly to Live" still get my blood pumping, imagine them with AH3 graphics. VuduVince has some great video tutorials, too.