The autonomous sub scouring the depths of the Indian Ocean for Malaysia Airlines flight MH370 was finishing up the last five percent of the target area on Sunday — having discovered nothing of interest after 14 dives — but that doesn’t mean the mystery will go unsolved forever, experts said.

“They have a lot more region that they have to be looking through,” said Van Gurley, retired U.S. Navy captain who specializes in oceanography and undersea research.

Even though the batteries on the Malaysia Airlines jet’s black box are almost definitely exhausted since the plane has been missing for more than 50 days, previous “ping events” provide leads that are still very much viable, Gurley said.