It's entirely possible that the interpretation of the pings that were stated as "definitely being from an aircraft", have now been thrown into doubt, since the hardware and software faults were discovered, both on the Bluefin-21, and on the Ocean Shield equipment.
Excerpt from news article dated 15th May -
"Examination of the communications problem has established that a hardware defect exists in the transponder mounted on the Ocean Shield, and a defect may also exist in the transponder mounted on the Bluefin-21," JACC said.
"This inhibits the ability of the two devices to communicate with each other."
The faults discovered may have led to a re-assessment of the interpretation of the pings recorded, that then placed serious doubt on what
was actually recorded.
If this is the case, then it's a major blow to the whole search exercise, that effectively throws the search effort back to almost square one.