The last time anyone saw the Boeing 777 used for Malaysia Air flight 370 was as it took off on a the evening or March 8, 2014, and vanished into one of the airline industry’s enduring mysteries. More than sixteen months later, experts increasingly believe that one piece of the airplane has emerged on the coastline of an island off the eastern Africa coast. The debris definitely came from a Boeing 777, Boeing confirmed, and CBS reports that only one Boeing 777 is missing at this time in the region:

Boeing has confirmed that the wreckage is wing part called a flaperon, and that the serial number found on it belongs to a Boeing 777 aircraft, CBS News correspondent Seth Doane reports, but French authorities are planning to send the piece to southern France for analysis before confirming it came from the missing Malaysian flight 370. The part could arrive Saturday morning, according to the Paris prosecutor’s office. …

Philippe Sidam, head of an association that maintains the Bois Rouge beach near where the aircraft wing was found Wednesday, says the ocean currents bring all kinds of debris. He displayed a laundry bottle from Indonesia, 4,100 miles away, as an example.

But after 16 agonizing months without answers, loved ones of those on board MH370 will likely have to wait at least another day, as investigators continue work to confirm the source of the barnacle-encrusted part.

All the signs are pointing to a positive identification. Captain “Sully” Sullenberger, CBS News’ aviation and safety expert, noted on “CBS This Morning” on Thursday that there is one missing Boeing 777 plane in the world right now: MH370.

If this turns out to be part of MH370, and that seems likely at the moment, it probably will do little to explain what happened, or even where the rest of the airplane is. One official quoted in the clip notes that it will eliminate some “fanciful theories” about the plane landing elsewhere and the passengers held hostage, but those theories have long been debunked anyway. The only way to solve the mystery of MH370 is to find the airplane and the recorders, but sixteen months of searches have turned up nothing at all. The flaperon is the first evidence of the plane’s existence since it disappeared off of radar screens nearly seventeen months ago.

Speaking of fanciful theories, the emergence of the debris prompted a revisiting of other hypotheses about the fate of MH370. ABC reported last night that the flaperon’s status appeared to show that it had been extended at the end of the flight, suggesting that the plane was attempting to either land or ditch at sea rather than experiencing a steep dive. Intelligence officials have other theories:

ABC US News | World News

U.S. intelligence agencies put together an assessment in the wake of the disappearance of Malaysia Airlines Flight 370 indicating that the plane was deliberately taken off course, according to a source with knowledge of the matter.

The assessment — made months ago and concerning what most likely happened to the plane — which disappeared in March 2014, also said that the Boeing 777 was also potentially deliberately downed, the source said.

However, according to the source, the assessment “doesn’t matter” and was built on information that intelligence officials could glean about the foreign investigation in the disappearance.

Both of these theories seem nearly as fanciful as those that the official dismissed in the CBS video. They may be correct, but one would think that it takes more than just one flaperon to determine the angle of entry into the ocean. As for deliberately going off course, that’s certainly a possibility, but without the flight data recorder and cockpit voice recorder, it’s just speculation. (The transcript of the air-traffic control conversation has one curious anomaly but no other evidence of foul play.)

For now, the mysteries of Malaysia Air 370 remain, and will at least until the first mystery gets solved: where is it?