On the surface, the discovery on a Reunion Island beach is just what investigators have been waiting for -- the first physical piece of evidence since the flight vanished en route to Beijing in March 2014 with 239 people aboard.
According to a source close to the investigation, Boeing investigators are confident the debris comes from a 777 aircraft -- although no one is yet saying the part came from Malaysia Airlines Flight 370.
But what's taking so long?
A complex investigation
Because Reunion Island is a French territory, the debris has been flown to France, where aviation safety bureau the BEA has taken responsibility for its testing and analysis.
The flaperon arrived in Toulouse over the weekend, but the fact that so many different countries and groups are involved in the search for the missing flight has complicated and delayed the situation somewhat.
Aviation experts are not expected to begin examining the part until Wednesday, and it is unclear how long their analysis will take.
Teams from each of the nations taking part in the search are expected to attend. Malaysia Airlines is sending investigators to France and a second team to Reunion, an airline official said.
Mary Schiavo, a CNN aviation analyst and former inspector general of the U.S. Department of Transportation, said those involved would be careful to make sure all tests were carried out scientifically, and completely by the book.
She said that while "everyone knows that it most likely is from MH370," investigators do not want to jump to conclusions.
"They're going to do a lot of analysis on the part, everything from X-rays to sonograms," Schiavo said. "Then when they finally cut it open (looking for serial numbers and part numbers), it has to be filmed, all the parties to the investigation -- there are seven nations in this investigation -- they all need to be present."
David Gallo, of the Woods Hole Oceanographic Institution, agreed: "That's the way the BEA -- the French version of the NTSB -- works; they will be very careful about what they say and don't say.
"It's going to be scientific. It's a piece of evidence in a criminal investigation at this point, so they're going to take it apart bit by bit."
Identifying the wing fragment
Planes are stamped with serial numbers to allow parts to be identified and matched to a specific model and aircraft.
A source close to the investigation said Boeing investigators feel confident the piece comes from a 777, based on photos that have been analyzed, and a stenciled number that corresponds to a 777 component.
Another source told CNN's Rene Marsh that Boeing engineers have seen a part number in photos. A parts supplier confirmed 10-60754-1133 is a part number on a seal associated with 777s.
Images of the debris also appear to match schematic drawings for the right-wing flaperon from a Boeing 777. A flaperon helps the pilot control the aircraft.
"If the part numbers that are stamped on the pieces of the plane still survive, it literally could be a phone call to Boeing or the parts indices to see if it belongs to a 777. And if it belongs to a 777, it is MH370," said Schiavo.
Of the five accidents involving Boeing 777s, MH370 is the only one in which debris hasn't been recovered, Schiavo said.
If the identifying numbers are missing, more tests will need to be conducted on the part to determine its origin.
A French laboratory that the BEA could use has the capacity to "identify very quickly" which plane the debris belongs to, and what happened to it, a source close to the French investigation said.
Australian investigators, heavily involved for some time in the search, said they are looking at the barnacles attached to the discovered part that could allow marine biologists to tell how long it has been floating.
Truss said that he understood "the photographs that are available are of such detail that it may be possible to make an identification without further physical examination."
What does the condition of the debris indicate?
Through the French laboratory near Toulouse, "engineers would be able to identify quickly whether the plane exploded in the air or whether it broke when hitting the water," the source close to the French investigation said.
Images of the component appear to show a small amount of damage to the front of the flaperon and a ragged horizontal tear across the back.
One group of independent observers has said that the damage to the flaperon should give authorities a good indication that the piece came off while the plane was still in the air.
The rear damage could have been caused if the airliner had its flaperon down as it went into the ocean, some members of the group, led by American Mobile Satellite Corp. co-founder Mike Exner, wrote in a preliminary assessment.
But the lack of damage to the front makes it more likely the plane was in a high-speed, steep, spiral descent and the part fluttered until it broke off, the group said.
If the flaperon were still on the wing when the plane hit water, the front would have been damaged by hitting the part of the wing to which it was attached, the group says.
Others have offered differing opinions.
"It really is not going to tell us too much about the final moments of the aircraft," said Geoffrey Thomas from AirlineRatings.com
However, Tom Ballantyne of Orient Aviation magazine said the condition of debris could indicate if the plane met a catastrophic end. Charring, for example, could indicate an explosion, he said.
Sciavo said investigators would be on the look out for tell-tale signs of what caused the crash: "It's possible to find positive evidence of a criminal act, or, of course they could find the absence of that.
"If they find characteristic pitting in the wing structure, in the metal or the composite, that indicates there was some sort of explosive device, or if they find residue, which is not likely (after) this long in he ocean," she said.
"But they'll probably not be able to tell why the plane went down -- only that it did, and the manner in which it did."
To learn more, the flight data recorders -- or so-called black boxes -- will be crucial.
If it is from MH370, will the main search area move?
Truss told a press conference Friday that the discovery of the debris in Reunion was "consistent with some of the modeling we've done."
"We remain confident that we're searching in the right place," he said.
He said authorities would "continue to concentrate our efforts on seeking to locate the aircraft in the identified area."
The current search is focused deep in the ocean off Western Australia, along an arc considered by investigators to be the most likely area the plane went down if it turned back toward Malaysia, as indicated by data, and stayed in the air before running out of fuel.
The southern end of the search area was the main focus, Truss said, but during the winter months weather conditions at that latitude were poor.
Once that search was completed, he said, searchers would focus efforts on a second identified area of interest.
If it's part of the plane, is it more likely the main section will be found?
Truss said no.
Truss said that if the flaperon is proven to be from MH370, its discovery did not "provide a great deal of help in specifically identifying where the aircraft is."
If confirmed, however, the find is likely to give investigators further belief that other pieces of the plane have been carried by currents to the same region.
Will debris lead to a rethinking of past theories?
Thomas said, if anything, the location of the potential debris confirms modeling from the University of Western Australia that showed material from the plane could wash up around Reunion between 12 to 24 months after the plane's disappearance.
Despite the modeling, no one had been searching in that area, he said, because of the vast nature of the Indian Ocean and the multitude of factors that meant finding anything would be matter of luck and time.
"It was a matter of waiting for something to wash up," he said.
However, Truss said, a positive identification with MH370 would rule out the some of the more left-field theories that the aircraft was "secretly parked in some hidden place" on land.