"To me, it is a helpless day as doors are shut," said one family member.
"This was planned, this was deliberate, and it was done over an extended period of time," Martin Dolan said.
Ocean Infinity will resume the search on a "no cure, no fee" basis, meaning the team will only receive payment if it is able to locate the plane.
The search lasted three and a half years and was the most expensive in history.
The information gleaned should provide unprecedented insight into the habitats of valuable species.
If his theory is correct, investigators may be looking in the wrong search area.
In total, authorities have found five pieces of wreckage believed to be from the plane.
The two-year search has now discovered two shipwrecks, but still no plane.
An Air France pilot on Tuesday reported seeing an object floating in the water near Réunion Island in the Indian Ocean.
After initial confusion, the French confirmed the flaperon is from the missing plane.
About 30 relatives marched to the Malaysian Embassy in Beijing on Friday.
Officials couldn't immediately confirm whether the fragments belonged to Malaysia Airlines Flight 370.
The wing fragment found last week on Reunion Island was confirmed to be from Malaysian Airlines Flight 370.
The debris washed up on the Indian Ocean island of Reunion and could help end 16 months of lingering uncertainty.
The beacon battery for the flight data recorder expired in December 2012 and was not replaced.
A year on from the disappearance of Malaysia Airlines Flight MH370, an extraordinary amount of key data remains unknown.
The Boeing 777 aircraft disappeared on March 8 2014, carrying 239 passengers and crew shortly after taking off.
A Dutch firm will lead the search, the next phase of which is expected to start within a month and take up to a year
The passengers and crew of the missing Malaysia Airlines Flight MH370 most likely died from suffocation and coasted lifelessly into the ocean on autopilot
The new analysis comes more than 100 days after the Boeing 777, carrying 239 passengers and crew, disappeared on March 8 shortly after taking off