They were words heard around the world as investigators searched for the missing Malaysia Airlines plane.

Weeks ago, Malaysian authorities said the last message from the airplane cockpit was, "All right, good night."

The sign-off to air traffic controllers, which investigators said was spoken by the plane's copilot, was among the few concrete details officials released in a mystery that's baffled investigators since the Boeing 777 disappeared with 239 people aboard on March 8.

There's only one problem. It turns out, it wasn't true.

On Monday, Malaysia's Transport Ministry said the final voice transmission from the cockpit of Flight 370 was actually "Good night Malaysian three seven zero."

Malaysian authorities gave no explanation for the discrepancy between the two quotes. And authorities are still trying to determine whether it was the plane's pilot or copilot who said them.

The new language is routine and is not a sign that anything untoward occurred aboard the flight, said CNN aviation analyst Mary Schiavo.

But the change in wording weeks into the search for the missing plane raises questions about how Malaysian officials have handled the investigation.

"It speaks to credibility issues, unfortunately," Schiavo said.

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

Malaysian authorities have defended their handling of the situation.

Acting Transportation Minister Hishammuddin Hussein said Monday that authorities were not hiding anything by declining to release some details of the missing flight. Some details are part of ongoing investigations into what happened to the plane, he said.

"We are not hiding anything," he said. "We are just following the procedure that is being set."

Long search ahead

The search for what happened to Malaysia Airlines Flight 370 "could drag on for a very long time," the chief coordinator for the agency organizing the efforts said Tuesday.

"It's not something that's necessarily going to be resolved in the next two weeks, for example," said retired Air Chief Marshal Angus Houston, chief coordinator of the Joint Agency Coordination Centre. The center was established on Monday and was in "setting up mode" on Tuesday.

The search area for the plane is extremely broad, "the like of which we probably haven't seen before," Houston told reporters Tuesday. But "our expectation is that it crashed into the southern (Indian) Ocean."

On Tuesday, 10 military planes, a civilian jet and nine ships are taking part in the Indian Ocean search, which spans a swath west of Perth that's 120,000 square kilometers (46,300 square miles), officials said.

The last known position for MH370 was around the Malacca Strait. But the plane apparently flew for several hours after that, and "that's the problem," Houston said.

"Essentially, we do not have any precision in where the aircraft entered the water."

Source: Plane's turn considered 'criminal act'

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

And 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."

Several friends of Capt. Zaharie Ahmad Shah said they refuse to believe he could have been the "criminal" controlling the plane.

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.

Several leads dry up as search ramps up

Potential leads on the missing Malaysia Airlines Flight 370 keep coming. So do the setbacks and frustrations.

Weeks of searching have yielded nothing. "What we really need now is to find debris wreckage from the aircraft, and that will change the whole nature of our search because we will then be able to employ high technology to help assist us with the underwater search," Houston said.

Monday's search ended without finding anything significant, Australian officials said. Four orange objects spotted by search aircraft and earlier described as promising turned out be nothing more than old fishing gear, they said.

U.S. Navy officials loaded underwater locating gear aboard an Australian naval ship and set out to sea Monday evening, but won't be able to use the equipment until investigators narrow the search zone.

The gear includes a pinger locator that's towed behind a ship and scans for the sound of the locator beacon attached to the plane's flight data recorder. Also onboard is an underwater drone that can scan the ocean floor for debris.

It will take the ship, the Ocean Shield, three days just to get to the search zone, leaving precious little time to locate the plane's flight data recorders before the batteries on its locator beacon run out. The batteries are designed to last 30 days; the plane has been missing for 24 days.

Under favorable 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.

In this case, searchers barely know where to look at all.

Late last week, the search area shifted more than 600 miles after what authorities described as "a new credible lead." But a Wall Street Journal report Monday night, citing anonymous people familiar with the matter, said before that crews had searched for three days in the wrong location due to "lapses in coordination among countries and companies" trying to find the missing jet.

What happened? Andy Pasztor, one of the reporters who wrote the story, said it boiled down to poor coordination between two parts of the investigation: one dealing with satellite data, and the other one dealing with fuel consumption and aircraft performance.

"And so what we're left with is sort of a three-day gap where it's clear that folks were definitely looking in the wrong place," he said.

Relatives' demands

Family members of people onboard Flight 370 have accused Malaysian officials of giving them confusing, conflicting information since the plane vanished more than three weeks ago.

On Monday, dozens of Chinese family members visited a Kuala Lumpur temple. They chanted, lit candles and meditated.

"Chinese are kindhearted people," said Jiang Hui, the families' designated representative. "But we can clearly distinguish between the good and evil. We will never forgive for covering the truth from us and the criminal who delayed the rescue mission."

Hishammuddin said Malaysia will hold a high-level briefing for families where experts will explain some of the data and methodology used to guide the search.

He also said authorities have discussed with the families what happens if they are unable to find debris from the missing plane. But he declined to discuss it with reporters Monday, saying "to be fair to the families, that is something I would not want to share with the public at the moment."