Market leader is Aircell, providing services to the likes of American, Delta, Airtran and many others.

According to Aircell, 1,009 commercial aircraft are equipped with wifi access from Aircell called GoGo Inflight Internet.

Meanwhile, Row 44 announced this week that it has raised $37 million, this only eight months after Aircell raised $176 million.

While others use ground based antennas, Row 44 leases telecomm satellites which can provide wifi access globally.

This is great news for the aviation industry as well as for passengers. Wifi is therefore perhaps the killer ancillary that people are actually prepared to pay for without feeling cheated.

Keeping passengers occupied with stuff that matters to them most will have them using their plastics like never before.

The ancillary business in aviation is exploding and last year the global airlines made more than $13 billion. Inflight wifi is so far a minimal revenue source.

But, lest we forget, so were check-in fees and other forms of ancillaries in the beginning.

Delta, American, Alaska, Air Canada, AirTran, Frontier, United, US Airways and Virgin America are among Aircell’s customers.

Clearly, Aircell, which has a cell-tower network covering the continental U.S., is the dominant provider of Wi-Fi to mainline aircraft (as opposed to regional jets) in North America.

Slowly, Wi-Fi will become ubiquitous.

Aircell says it will continue to bolster Gogo’s client based in 2010 and will install the service on more jets. Currently 3,800 flights daily have GoGo Wi-Fi service, and that’s up from 2,100 flights a year ago.

Waiting in the wings is satellite-based Row 44, which counts Southwest as its only U.S. customer.

However, Southwest, the largest U.S. domestic airline, has some 540 aircraft and Row 44 is slated to have the entire fleet Wi-Fi-enabled in 2013.

Aircell and Row 44 battled over the Alaska Air account, with the carrier running tests of both systems, and ultimately chose Aircell a few months ago.

Aircell says it installed Gogo service in numerous Alaska, Delta and American jets in August.

Row 44 seems perplexed about Alaska’s choice of Aircell.

“They chose a few months back to switch to Aircell,” says Row 44 spokesman Robbie Hyman, referring to Alaska. “Given the importance of their over-water routes, and the fact that Aircell cannot support those routes as fare as we know because their system requires constant contact with cell towers on the ground — hard to come by over the ocean — we do not know why Alaska chose this move.”

Alaska spokesperson Bobbie Egan says: “Aircell has a proven track record of deploying affordable inflight Wi-Fi services to airline customers. Its lower-cost equipment, coupled with the ease and speed of installation and finally its system reliability, allow Alaska Airlines to rapidly deploy the service to our customers.”

So Row 77, which says it is targeting airlines globally,  is playing catch-up with Southwest as a big client in the U.S. market and also claims its business model allows for more differentiation for clients.

Row 44, Hyman says, enables clients to brand their own Wi-Fi service and customize their own content while with, Aircell, “American offers the same Gogo service as Delta.”

Sounds good, but in the U.S. market, at least, the majority of carriers with Wi-Fi have opted for Aircell.

Southwest chairman and CEO Gary Kelly laid out this timetable during the company’s second quarter earnings call today after the company announced it recorded net income of $112 million, a 23.1% increase compared with the second quarter of 2009.

Kelly said he feels “very comfortable” with the “2013 timeframe” for fleetwide Wi-Fi installation even as the company works on several initiatives to increase its hold on business travelers.

Southwest, the largest domestic carrier in the U.S., began testing Wi-Fi service from vendor Row 44 in late January 2010, and at the time the airline indicated that all its aircraft would have Wi-Fi capabilities by “early 2012.”

In the airline’s most recent edition of Spirit Magazine, Kelly wrote that the airline began the two-year installation process in April 2010 — which would have made full implementation scheduled for around April 2012.

But, today Kelly said the certification process has been taking longer than expected and the airline is looking at the “2013 timeframe” to complete the process.

Meanwhile, Kelly said the airline has a “very significant” opportunity to win more business customers and it plans to implement significant changes to its Rapid Rewards program, including the Rapid Rewards Visa credit card component, in 2011.