These days, you’re lucky to get a free bag of peanuts on an airplane. But on Tuesday, low-cost airline JetBlue Airways began testing an in-flight Internet service that lets passengers check their e-mail for free.

I was on the maiden voyage — an Airbus A320 painted with the logos of JetBlue partners Yahoo and Blackberry maker Research in Motion (RIMM) that took off Tuesday morning from New York’s JFK airport bound for San Francisco. A few days earlier, JetBlue (JBLU) had invited a handful of reporters aboard the same plane, but this was the first commercial flight to offer Internet access within the United States.

Once the airplane reached an altitude of 10,000 feet, we were allowed to turn on our laptops and Wi-Fi enabled Blackberry smartphones and connect. It took me several tries, but a few minutes later I was able to log on to the simplified Yahoo Mail interface on my browser. After that, it was easy to send and receive e-mails.

The biggest drawback is that the service only lets passengers access Yahoo’s (YHOO) e-mail and instant messaging. Still, it’s hard to complain about a free service and many passengers aboard the flight tested the Internet service with their laptops or Blackberries.

David Kubersky, a tech consultant from New Jersey who flies JetBlue regularly to the San Francisco Bay Area, said the company’s Internet service was a little bit slow but most of his e-mails went through easily.

“Usually this is my time to catch up on TV,” said Kubersky, pointing at the small seatback screen in front of him. “But it’s nice to be able to have some form of communication back to the ground.”

Henry Harteveldt, an analyst with Forrester Research also aboard the inaugural flight, said he was optimistic about the service, which will eventually expand to include access to other e-mail services.

Then again, the current lack of full-blown Internet services (which translates to lower bandwidth needs) is partly how JetBlue is able to keep it free of charge to consumers. In the future, you can expect to see an ad-subsidized model and maybe a “premium” subscription that gives paying customers complete online access, said Mike Moeller, VP of spectrum services for LiveTV, a JetBlue subsidiary and the provider of the airline’s Internet service.

This isn’t the first — or the last — time an airline has attempted to offer Internet access from the friendly skies. Airplane maker Boeing (BA) took a stab at it for six years before folding its Connexion service in August 2006 on the grounds that the market had “not materialized as had been expected.”

But Harteveldt said Boeing’s failure was most likely due to pricing and timing issues. (Boeing used an expensive satellite system to deliver wireless Internet access and launched right before 9/11).

“Boeing builds great airplanes, but they’re not a marketing organization,” said Harteveldt.

JetBlue, meanwhile, is relying on about 100 cell towers across the country that communicate with radios onboard the plane (LiveTV paid $7 million for its own slice of wireless spectrum last year). The in-flight Wi-Fi network is activated by three wireless access points hidden in the roof of the plane.

LiveTV CEO Nate Quigley said that whatever evolutions the service goes through, there will always be a free component to the service.

“There have been a bunch of false starts, but the business model never worked” says Quigley. “You shouldn’t have to pay to send a message to your wife saying you’re going to be late because you’re circling the airport.”

Free e-mail access — however limited — isn’t bad for keeping in touch with work, family and friends while at 30,000 feet. That is, of course, if your hard drive doesn’t crash mid-flight, as mine did.

American, Virgin and Alaska Airlines have also said they would soon launch their own in-flight Internet service, though they have not disclosed details on pricing.