Are you gaga for Gogo inflight wi-fi?

To me, Gogo’s introduction of in-flight wi-fi in 2008 was the greatest thing to happen to business travel since the invention of the jet engine. It has so transformed the flying experience that I now choose my airline based on whether or not it offers wi-fi on board—especially if the flight is longer than two hours.

But recently it seems that the more popular in-flight wi-fi gets, the more difficult is to get a good signal, especially on those long transcontinental flights when the service is most valuable. For example, on two out of three recent transcontinental flights, the signal was so weak or inconsistent that I complained to Gogo, which offered me two $18 credits for use on future flights.

Obviously, Gogo does not want to keep handing out freebies like that, so they’ve fattened the pipes to the plane with the introduction of a new higher capacity system called ATG 4, which is rolling out now on Delta, Virgin America and US Airways jets.

Gogo says the next generation system is capable of delivering a peak speed of 9.8 Mbps, which is three times faster than current standard of 3.1 on the first generation ATG. (ATG is short for “Air to ground.) Gogo is able to do this with the addition of three extra antennae (vs. only one before) and another modem plus a software upgrade.

Gogo’s inflight internet lab (See slideshow for a look inside)

Earlier this week, Gogo invited me and a few travel and tech writers to its headquarters in Itasca, Il to check out the new ATG 4 system aboard its “jet-propelled internet lab” — a Challenger 600 jet flying out of the Aurora Municipal Airport near Chicago.

Onboard the plush 9-seater, the back half of which was full or racks of equipment and cabling, I heard lots of techno babble about latency, megahertz, simulations, Rev A and Rev B, HSPA Mbps, ping tests and page loading. All way over my head.

All I cared about was whether or not I got a good signal—and on this flight I did—good enough to stream a two-minute YouTube video with only a few bumps for buffering, even though Gogo now discourages or even blocks access bandwidth hogging sites like Hulu or Netflix. But there were only nine passengers on board flying over the western suburbs of Chicago.

It remains to be seen what kind of signal I’ll get using ATG 4 the next time I’m flying over Colorado when half the plane is logged on.

Right now, there are only 25 jets that have the new ATG 4 system—out of a total of 1680 jets flying with Gogo onboard.  Gogo is not making a big deal about the upgrade on the plane– the only way you know you are on an upgraded one is by taking a good look at the plane parked at the gate—look for two fins on the underbelly (vs. just one on the bottom before) , and two directional antennae (bicycle helmet sized humps) on either side if the aircraft fuselage. (See slideshow above for a look at these fins)

Currently, installation of ATG 4 is ongoing on Delta, Virgin America and US Airways. Gogo expects to add it to United’s PS fleet and on American Airlines starting next year.

Here are a few extra newsy nuggets I picked up on my visit to Gogo HQ and the test flight:

>There are currently 173 ground-based Gogo transmitters mounted on celluar towers in the continental US and southern Alaska that beam up a signal within a 250 mile radius.

>Gogo is adding and upgrading its transmitters fastest in the Midwest—which is where most complaints about weak signal occur.

>A Gogo system onboard a plane consists of two large toaster-sized black metal boxes mounted in the belly, two or three routers (about the size of the one you may have in your house) that are placed in the ceiling of the aircraft to evenly distribute the wi-fi signal among passengers, and lots of cabling. Total added weight is about 150 lbs.

>The new ATG 4 system can handle about 65 passengers logged on simultaneously—the current max is about half that. This means that overload problems are more likely on larger planes flying on longer routes– for example, both of my poor connection experiences occurred on 250-seat Delta 767s.

>Remember when Google sponsored free inflight during the holidays in 2009? So many users logged on that systems crashed and complaints soared. Gogo says that after that, freebie promos have been (and will continue to be) limited to short 15 minute test periods only.

>While overall in-flight wi-fi usage stats sound low (at around 5%), Virgin America says that usage runs as high as 40% on transcontinental flights, especially those between San Francisco and New York (natch).

What’s been your experience with in-flight wi-fi? Are you a heavy user like me? Have you experienced connectivity issues? Would you rather spend your time on board reading or gazing out the window? Please leave your comments below.