After 25 days, plenty of ocean trash and questions, but no sign of Flight 370

Kuala Lumpur, Malaysia (CNN) -- After more than three weeks, the search for Malaysia Airlines Flight 370 has come down to this: a lot of floating rubbish, hundreds of heartbroken relatives and, now, quibbling over words that everyone acknowledges offer no clues into what happened to the doomed plane.

Malaysian authorities on Tuesday released the transcript of radio chatter between air traffic controllers and the plane in the hour or so before it vanished while flying from Kuala Lumpur, Malaysia, to Beijing on March 8 with 239 people on board.

And while the transcript offers no clues about the plane's mysterious disappearance, one glaring discrepancy has highlighted criticisms of how Malaysian officials have handled the investigation.

Read the cockpit transcript

Looking to past for Flight 370 answers

Australia: 'The search area is very large'

MH370: Malaysian investigation failures

The transcript shows the last voice transmission from the doomed plane was "Good night Malaysian three-seven-zero," not the "All right, good night" transmission authorities had previously used.

That authorities had given such an incorrect version earlier this month and allowed it to stand uncorrected for weeks undermines confidence in the investigation, air accident investigation experts told CNN.

"High criticism is in order at this point," said Mary Schiavo, a CNN aviation analyst and former inspector general for the U.S. Department of Transportation.

Malaysian officials have defended their work. Acting Transport Minister Hishammuddin Hussein recently said, "History will judge us well."

But Michael Goldfarb, a former chief of staff at the Federal Aviation Administration, said people following the investigation "haven't had a straight, clear word that we can have a lot of fidelity in."

"We have the tragedy of the crash, we have the tragedy of an investigation gone awry and then we have questions about where we go from here," he said.

Inside the flight simulator

Search 'could drag on'

And where we go from here is a very big question.

After refocusing their search Friday to a new patch of Indian Ocean hundreds of miles from where they had been looking, authorities still haven't found anything definitively linked to Flight 370.

Official: We're in the right place

Sources call MH370 turn a 'criminal act'

Ten aircraft and nine ships crisscrossed a 46,000-square-mile (120,000-square-kilometer) search zone on Tuesday. As of early Wednesday morning, Australian search coordinators had not announced any significant results.

With so many planes in the skies over the search zone, Australia sent an airborne air traffic control plane to guard against accidents.

Australian officials have vowed to keep up the search off their west coast, an effort the head of the country's new Joint Agency Coordination Centre warned could take time.

"It's not something that's necessarily going to be resolved in the next two weeks, for example," retired Air Chief Marshal Angus Houston told reporters Tuesday.

The plane disappeared over the waters between Malaysia and Vietnam, after signing off with Malaysian controllers but before checking in with their counterparts in Vietnam.

Authorities don't know what happened on board after that, but radar and satellite data show the plane turned off course and flew back across Malaysia before turning south over the Indian Ocean.

Based on sophisticated analysis of satellite data, investigators believe it went down in the southern Indian Ocean, but can't pinpoint a precise location.

A Malaysian government source told CNN on Monday that the airliner's turn off course is being considered a "criminal act," either by one of the pilots or someone else on board.

In a background briefing given to CNN, Malaysian investigators said they believed the plane was "flown by someone with good flying knowledge of the aircraft."

Clock ticking on search for Flight 370

Timeline of the hunt for Flight 370

Officials revise last words from MH370

A senior Malaysian government official last week told CNN law enforcement analyst Tom Fuentes that authorities have found nothing in days of investigating the two pilots that leads them to any motive, be it political, suicidal or extremist.

More help on the way

Hishammuddin tweeted that he'd learned Tuesday that the HMS Tireless, a British nuclear submarine, is joining the search.

It will have plenty of company, including an Australian ship with a pinger locator designed to listen for locator beacons attached to the plane's flight data recorder plus a submersible capable of canvassing the ocean floor for wreckage. Both pieces of technology come from the U.S. Navy.

The equipment won't be of any use, however, until searchers are able to find wreckage from the plane to help narrow the search zone.

That's because neither the pinger locator nor the submersible can quickly scan the enormous area being searched.

Under the best of sea conditions, the pingers can be heard 2 nautical miles away. But high seas, background noise, wreckage or silt can all make pingers harder to detect.

It will take the ship, the Ocean Shield, two more days just to get to the search zone, leaving precious little time to locate the flight data recorders before the batteries on its locator beacon run out.

Time is running out: The batteries on the flight data recorder's locator beacon are designed to last 30 days. The plane has now been missing for 25.

Chinese relatives of the passengers, meanwhile, are being offered a chance to meet with technical experts to learn how they're searching for the plane and how they've concluded the flight ended in the Indian Ocean.

Malaysia Airlines and Malaysia's Department of Civil Aviation will lead a closed-door briefing with the Chinese relatives in Kuala Lumpur on Wednesday, the Malaysian government said. Technical experts from Malaysia, China and Australia will also participate in the briefing, as well as the Chinese ambassador to Malaysia.

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Michael Pearson reported and wrote from Atlanta; Jim Clancy reported from Kuala Lumpur; CNN's Catherine E. Shoichet, Holly Yan, KJ Kwon, Barbara Starr, Will Ripley, Greg Botelho, Richard Quest, Nic Robertson, Sara Sidner, Mitra Mobasherat, Kyung Lah and Yuli Yang also contributed to this report.