For 17 months, Malaysia Airlines Flight 370 was, in a sense, nowhere. The lack of any tangible clue to its fate was eerie, unsettling, bizarre — a real-world echo of the TV show "Lost" and the wayward-jetliner mystery at the heart of its story.

With the Malaysian prime minister's announcement Thursday that a wing fragment found on an Indian Ocean island belongs to the missing plane, the mystery has changed. Less Bermuda Triangle or Amelia Earhart; more Air France 447, which crashed into the Atlantic in 2009 but confounded investigators for nearly two years until its black boxes were found.

Though other countries involved in the investigation make the point less emphatically than Malaysia, all agree the wing piece appears to be from Flight 370, lost March 8, 2014, on its way from Kuala Lumpur to Beijing with 239 people on board.

So we know it ended up in the ocean. We just don't know why. What does that change, if anything?

"The appearance of at least some wreckage takes it out of the realm of 'vanished without a trace, cue the music,' with 'OK, sure, it did go down in the ocean,'" said Ric Gillespie, a former U.S. aviation accident investigator who wrote a book about Earhart's still-unsolved 1937 disappearance over the Pacific Ocean. "It's an aviation accident."

Before the discovery of the wing piece on the French island of Reunion, experts generally agreed that the Boeing 777 crashed in a remote stretch of the Indian Ocean. But with no physical evidence, no one could say so with certainty. And there were nagging suspicions that the experts got it wrong. Did the plane fly north to Asia, rather than south into the ocean? Could those on board even be stuck on some far-flung island, like the characters on "Lost"?

Australia's prime minister, whose country is leading the search for the plane in a desolate stretch of ocean 4,200 kilometers (2,600 miles) to the east of Reunion Island, said the discovery provides at least one piece of the puzzle.

"What we have found in the western Indian Ocean does seem to indicate that the plane did come down more or less where we thought it did," Tony Abbott said. "And it suggests that, for the first time, we might be a little bit closer to solving this baffling mystery."

Yet in many ways, the mystery only deepens from here. Discovering the wing piece is not expected to help narrow the vast body of ocean where the search for the main body of the plane continues.

Investigators examining the wing fragment in France are trying to glean clues into the plane's fate based on its condition, opening up even more questions: How, exactly, did the plane end up in the water? Was it a controlled landing? Was there an explosion? Who did this, and why?

Officials who scrutinized data exchanged between the plane's engine and a satellite determined that the jetliner took a straight path across the ocean, leading them to believe that the plane flew on autopilot for hours before running out of fuel and crashing into the water.

But there are plenty of other theories, and news of the wing flap's discovery did little to quash them. After Malaysian Prime Minister Najib Razak's announcement, online commenters immediately began debating whether the flap could have been planted on the island by terrorists, or whether the plane landed on Diego Garcia, a British atoll in the Indian Ocean where the U.S. has a military base.

Such speculation is unlikely to stop, Gillespie said, unless officials find the plane's coveted "black boxes" — the data and cockpit voice recorders.

"If it's anything like the Earhart thing, nothing deters a conspiracy theorist," he said.

For the families of those on board, the transition of the plane's mystery from nebulous to slightly more tangible does little to relieve them of the emotional limbo they've endured since the plane vanished last year.

Many relatives expressed frustration that Najib spoke more unequivocally than authorities in France, the U.S. and Australia who identified the part as from a 777. Unlike Najib, those officials did not positively identify the piece as being from Flight 370, though they said it almost certainly was, given that no other 777s are missing.

For some families, only the recovery of a body will bring any semblance of closure. But the discovery of at least one part of the plane marks a step in that direction, said Angela Crawford, a senior manager with New Zealand agency Victim Support, which offers counseling services to those affected by air accidents.

"It's a long journey; it's a piece of a wing," Crawford said. "It's starting to bring that realization to them that they may be heading towards more understanding and closure, which can only be helpful."

Overall, though, officials were relieved that there finally seemed to be something concrete to cling to in what has been one of aviation's most confounding mysteries.

"At least it is a piece of evidence," Australian Foreign Minister Julie Bishop told reporters in Kuala Lumpur. "I remember early on, somebody said it is not as if we are looking for a needle in a haystack — we are still trying to locate the haystack. This gives us some indication that we are in the right place."