Wi-Fi, now regarded as an amenity by U.S. airlines, might become a passenger necessity once Delta Air Lines, Inc. finishes an ongoing test that provides free in-flight Wi-Fi for passengers.

There is one catch, however. Delta only plans to offer basic Wi-Fi and this means no streaming will be allowed. U.S. domestic carriers currently charge for Wi-Fi use on their flights. Delta and United Airlines charge $7 for Wi-Fi access on domestic flights.

Delta Air Lines started a two-week pilot test on May 13 with free Wi-Fi on around 55 domestic short-, medium- and long-haul flight segments a day.

"Customers are accustomed to having access to free Wi-Fi during nearly every other aspect of their journey, and Delta believes it should be free when flying, too," said Ekrem Dimbiloglu, Delta's director of onboard product. 

"Testing will be key to getting this highly complex program right - this takes a lot more creativity, investment and planning to bring to life than a simple flip of a switch."

He said the test flight segments change daily. Passengers only are known if they're on a free Wi-Fi flight from a pre-flight email or via a push notification from the Fly Delta app. Gate agents and flight attendants also make the announcement.

Delta clarifies only free basic Wi-Fi is offered as part of the test. Passengers that need to stream videos will have to pay for this service. Delta charges $16 for a North America Wi-Fi day-pass on if purchased pre-flight.

Aviation industry analysts said millennials and the younger generations expect free Wi-Fi access everywhere, especially when they travel.

"It's nice to see an airline offering a desired amenity on a complimentary basis," said Henry Harteveldt, travel industry analyst and Atmosphere Research Group founder. "But I'm uncertain whether Delta will be able to increase its market share, customer preference or revenue premium enough to warrant offering the free Wi-Fi."

Other industry analysts believe other airlines will have no choice but to follow suit.

"Delta tends to go first with these kinds of customer-friendly initiatives," said Seth Kaplan, an aviation journalist."

Kaplan said American Airlines and United sometimes match Delta rather than lose customers but Delta's move makes widespread free Wi-Fi much more likely than it seemed until recently.

In 2016, JetBlue became the first domestic airline to offer a free streaming-quality Wi-Fi service called Fly-Fi on all its planes.