If you booked a random domestic flight on July 6, you would have about a 60 percent chance of finding Wi-Fi onboard. The best bet overall would be to pick a Virgin America flight.
All of Virgin America's planes are equipped with upgraded air-to-ground antennas from Gogo (you're probably familiar with the company, which effectively founded the industry in 2008).
Those connections use similar technology to a 3G cell phone. They may be triple the speed of the first generation, but you shouldn't expect to be streaming any videos—the peak download speed is much slower than the average home or smartphone connection, and it has to be shared with everyone else on the plane.
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"Passengers are expecting more and more capacity, more and more bandwidth, just like they experience on the ground," said Steve Nolan, spokesman for Gogo.
Of course, while Virgin's 100 percent Wi-Fi coverage is impressive, the airline is tinier than the rest with only about 50 aircraft. Delta, which has more than 5,000 flights scheduled for the day tested, may be the most impressive overall with 80 percent coverage.
But most of the airlines are offering speeds that wouldn't satisfy today's user. Even Southwest, which uses a newer satellite system, doesn't offer high speeds—perhaps because the bandwidth isn't worth the cost.
For the fastest internet, a traveler should go with United or JetBlue. JetBlue, one of the last major American airlines to add Wi-Fi to its flights, uses satellite technology that can stream video, and it recently made a deal with Amazon for content.
United, which is the unique position of having three different internet providers, has the overall lowest chance of providing internet to our domestic traveler. The airline was slow out of the gate in adopting Wi-Fi, but it has focused on outfitting its entire fleet in recent months and has seen the most growth overall.