If you want to escape the Internet, taking flight will no longer be an excuse. Internet access has arrived on dozens of planes flying domestic US routes, with hundreds of aircraft across seven airlines expected to be online by the third quarter of 2009. Early reviews indicate that at least two competing in-flight Internet services work consistently and offer reasonable speeds.

In this article, we'll take an in-depth look into why WiFi up high failed once, and we'll examine the technology behind its recent rebirth. We'll also look at the cost of using the Internet at 35,000 feet, which airlines have made which choices, and what the future brings for entertainment and coverage.

Prologue: missed Connexions

Boeing pioneered mile-high WiFi with Connexion by Boeing, a service the firm started planning in the late 1990s that was poised to launch with a number of US carriers before 9/11 kicked the legs out from underneath the airline industry. American, Delta, and United had all planned to launch the service, but withdrew from their commitment.

Connexion's Irvine, Calif., operations center in headier times.

Although Connexion eventually got up in the air in 2004, with a new focus on mostly over-water and long-haul routes, the weight, installation time and cost, and apparently low revenue couldn't justify the service's continued operation, especially after major management turmoil at Boeing. In Dec. 2006, with Lufthansa as its biggest partner with dozens of equipped planes, Connexion shut down.

While Connexion's service worked quite well by all reports, its cost structure was out of control. Installation, at one point, took weeks (later shortened to days); the dead weight and drag of gear was estimated by some experts at about 800 pounds; and estimates varied from $500,000 to $1,000,000 for the full cost of equipment and installation.

At the same time that Connexion was taxiing to the gate, however, two firms were planning similar offerings that would use smaller antennas to reduce drag, lighter and cheaper gear in planes to reduce fuel costs, and a quicker installation process to roll planes out faster, while also taking advantage of the vast increase in the number of WiFi-toting passengers.

Since September 2008, several airlines have been slowly installing in-flight Internet service from these two companies. American was the first with a 15-plane trial, followed by fleet-wide commitments that began with planes operated by Virgin America in November, and then Delta in December. Alaska and Southwest launched long-delayed trials in February. United will run a small trial later in 2009, and Air Canada plans service for the U.S. portions of some of its routes. JetBlue has one aircraft wired using a previous-generation technology, but apparently has plans to change this in the future.

So what happened to change the cost/benefit equation for in-flight Internet? Airlines are desperate for ways to retain customers, while filling planes fuller and charging more for seats. Continuous Internet access might be both a competitive tool to capture passengers from other airlines, as well as a way to convince people to fly rather than stay home or take other transportation. So the coming wave of in-flight Internet is predicated on the premise that productivity and entertainment will be strong selling points.

Also, and just as important, every business traveler and an increasing number of consumers are carrying WiFi-enabled devices: BlackBerrys, laptops, iPhones, Nintendo DSs—the list goes on. They're just waiting to unwire.

The basics of broadband at 35,000 feet

Unlike many subjects that involve telecommunications, providing Internet service to a plane in-flight is relatively straightforward. You need an antenna on top of the plane for satellite services, or under the fuselage for ground-to-air offerings.

Onboard, WiFi access points provide the LAN. A gateway page sometimes provides portal information from a provider like Yahoo!, and it asks for either a purchase or the entry of credentials to use the network for paid rollouts.

A rack of gateway gear handles the WAN and LAN communication, and provide administrative tools to allow the flight crew to cut access. (This last option may seem extreme, but pilots are both allowed and required to take any necessary action in air to ensure safety, for whatever reason they determine.)

On the regulatory side, by the way, radio equipment installed on planes needs to be tested by the FAA or other local aviation regulatory agencies for airworthiness; the new gear, when installed, can't interfere with on-board electronics or avionics. Planes are certified by model, such as an Airbus A319 or Boeing 767-200. (Interference means, in this case, that typically spurious signals sent outside of assigned bands don't cause avionics to produce unexpected results. This likely occurs only with older planes using avionics that aren't as heavily shielded as newer systems.)

Three in-flight ISPs currently have planes flying with their hardware in them: Aircell and Row 44 in the US, and OnAir in Europe and the Middle East.

Fortunately for all those who prefer their flights as quiet as possible, no US airline allows voice over IP calling, voice chats, video chats, or any variant thereof. Aircell blocks well-known ports, and uses traffic shaping and other techniques to spot workarounds and block new methods as they're discovered. The FCC asked for opinions about this a few years ago, leaving a comment period open for years. Thousands of commenters begged the agency not to allow any form of in-air calling.

The FAA and FCC don't regulate what content people may view over an in-flight connection. Aircell and Row 44 are neutral, but airlines are not. After some initial back and forth between the flight attendant union and various airlines, American and Delta opted to have lightly filtered Internet service; Virgin America has no filters whatsoever. A VPN connection can bypass any filters, of course, and because this is a floating hotspot with no encryption against your data being sniffed, a VPN connection is a good idea in any case.