American Airlines apparently liked its long-running pilot test of Aircell Gogo Internet on 15 planes: The airline is expanding service over two years to 300 mainline craft. American has over 600 planes in its active mainline fleet, but about half those (Boeing 757, 767, and 777 models) spend most of their time over water, the carrier told the Dallas Morning News.

The company is opting for an interesting rollout: 150 MD-80s this year; about the same number in 737-800s in 2010. The first of the MD-80s with Gogo will go into service this week. The firm's 15 767-200s with Internet service used for cross-country routes will remain available, too.

The strategy is a bit odd: the expectation of service availability will likely be one factor that drives usage. Regular travelers will want to know that they can use Wi-Fi on a flight; otherwise, why would they change traveling preferences for a given flight without that assurance? I expect American might try to guarantee certain routes will have Wi-Fi, but it's still a bit odd.

Related to that, why stretch this over two years? Cost? I don't see how the company achieves a real competitive parity with Delta, which expects to have its domestic mainline fleet equipped by third quarter, without meeting Delta's fleet rollout.

Further Delta has signaled that it plans to announce a schedule later this year for putting Aircell's offering on domestic craft in the Northwest fleet that the airline acquired.

Delta reported on its blog a few days ago that it's at 77 planes with Internet service, or about 25 percent.