There has been other news on CNN lately — a little Ukraine here, a bit of President Obama there — but for the most part, there’s one story.

Since last week, several days after a Malaysia Airlines jet disappeared March 8, the network has packed hour after hour with news and talk about the missing flight. CNN has gone all in on the story — to the exclusion of almost everything else — while its cable news competitors have dipped in more sporadically.

The disparity in hours of coverage might be driven as much by each network’s strategic identity as by the news itself. The Malaysia mystery plays most to CNN’s brand as the go-to source for big international stories. Indeed, the jet story might illustrate why the cable news networks are actually niche networks — each with its own topical turf, perceived expertise and audience preferences.

“One of the key questions in the cable news business has been how you distinguish yourself from your competitors,” said Mark Jurkowitz, associate director of the Pew Research Center’s Journalism Project. “This [story is] the way to distinguish themselves, to be the 24-7 network when big news arrives.”

Whereas Fox News has catered to audiences interested in political news and talk from a conservative perspective and MSNBC has transformed itself into the liberal anti-Fox, CNN has struggled to find its place when the news is less captivating. For more than a decade, in the absence of major breaking news, CNN has often finished behind MSNBC in audience ratings — and occasionally even lagged behind its tabloid-y sister network, HLN, home of sensational trials. None of these news channels challenge Fox, which has captured the dominant share of the relatively small cable news market with its pugnacious prime-time hosts and intense skepticism of all things Obama.

Still, CNN competes best when major news breaks, particularly an international crisis or a natural disaster — or a mega-mystery such as the disappearance of a Boeing 777 in the skies over southern Asia.

Since the plane vanished, CNN’s overall audience has grown 86 percent among viewers ages 25 to 54 — the segment most coveted by advertisers — and by 71 percent overall, according to Nielsen.

Its ratings have far exceeded MSNBC’s but remain well behind those of Fox News, which was the top-rated network on cable during prime time in the week after the plane went missing. Even so, thanks to strong interest in the story, CNN managed a rare feat: It beat Fox during several hours Saturday and Sunday.

The promising ratings are at least partly a reflection of the fact that CNN’s competitors aren’t covering the missing jet as extensively as CNN is. The absence of direct competition also helped CNN last year when it covered the rescue of a disabled Carnival cruise ship in the Gulf of Mexico. The intense coverage of that story — CNN’s first all-out effort under new chief executive Jeff Zucker — was widely mocked but might have set the tone for CNN’s saturation reporting on other breaking stories, including the Boston Marathon bombing last April.

Fox and MSNBC have followed “all in” strategies, too, but on stories likely to play well with their audiences. MSNBC recently went nearly round-the-clock with discussion and news about the traffic scandal surrounding New Jersey Gov. Chris Christie (R); Fox devoted many hours to the technical glitches besetting, the Web site for the Affordable Care Act.

Sam Feist, CNN’s Washington bureau chief, said in an interview that the network was primed to cover the missing-jet story before the network calculated the ratings payoff. “You just know there’s a big story there,” he said. “This happens to be among the most compelling mysteries we’ve ever seen. At the same time, it touches so many areas that are important to American viewers — national security, potential terrorism, an American-made jetliner, a U.S. Navy search. There’s a technology story there and a dramatic human story involving 239 families. The public wants to know if their planes are safe.”

The relative success of the network’s approach to this story might leave CNN with a challenge in deciding when to stop covering it. Feist said the coverage won’t leave the air or the front page until the mystery surrounding the plane is solved. But the matter is “a day-by-day decision,” he said.

As the hunt for the missing jet expands across land and sea, here's a chronology of the baffling aviation mystery. (Gillian Brockell and Kate M. Tobey/The Washington Post)

“We look at the news environment with a fresh set of eyes every day,” he said. “If there’s news in other parts of the world, we’ll cover those stories, too.”