The British submarine HMS Tireless has arrived in the Indian Ocean on Tuesday night to help with the search for flight MH370. The vessel will help with efforts to find the plane's black box recorder in order to piece together its final moments, as a transcript of the last words spoken from the cockpit contradicts earlier reports on what the pilot said.

The submarine will search an area of around 98,000 sq miles off Perth, Australia. Royal Navy survey ship HMS Echo will also begin search efforts on Wednesday.

While the transcript revealed that the final message from the cockpit was not "All right, good night" as previously thought, it does not indicate "anything abnormal", authorities said on Tuesday.

The final words heard by Kuala Lumpur air traffic control were in fact: "Goodnight, Malaysian three seven zero," said Malaysia's civil aviation authority.

Nevertheless, the correction is likely to anger the families of those missing from MH370, particularly in China where there have been accusations that Malaysia has mismanaged the search and deliberately withheld information.

"We would like to confirm that the last conversation in the transcript between the air traffic controller and the cockpit is at 01:19 [Malaysian time] and is 'Goodnight, Malaysian three seven zero,'" the department of civil aviation said in a statement. It did not offer an explanation as to why the incorrect final words had circulated for weeks.

The transcript contradicts what Malaysia's ambassador to China told families in Beijing just a few days after the flight disappeared more than three weeks ago – and which was widely circulated in the media. The last words were said to have been a casual "all right, goodnight", indicating an unusual informality from the cockpit just minutes before its communications were cut and the plane veered from its Kuala Lumpur to Beijing route.

While Malaysia Airlines officials previously indicated the voice issuing the message was that of the co-pilot, investigators were still working with police and forensic experts to confirm this, the statement added

Malaysian authorities and international investigators still believe MH370's movements were "consistent with deliberate action by someone on the plane", the statement said.

Officials will on Wednesday share the transcript with the families of those missing today, at a closed-door briefing in Kuala Lumpur which the special envoy to China for Najib Razak, Malaysia's prime minister, is due to moderate.

Technical experts from Malaysia, China and Australia were expected to participate in the meeting. But British experts from Inmarsat, the satellite company which concluded that the plane most likely went down over the southern Indian Ocean, will not be part of the briefing.

Inmarsat told the Guardian that it had not been invited to attend the meeting. It said the company was not deliberately withholding information from the public. This comes amid mounting frustration that experts and officials were being evasive after Malaysian authorities claimed Inmarsat had been invited to speak last week to Chinese families in Beijing but declined. At the briefing, Chinese families hit out at Inmarsat and the UK Air Accidents Investigations Branch and questioned the analysis of the plane's location because no passengers and no debris had been found.

"It is not true that we refused to take part in a briefing last week," said Chris McLaughlin, Inmarsat's vice-president for external affairs. "I assume that that was just a degree of confusion because it is a very difficult thing that they [the Malaysian authorities] are doing. We hadn't been invited."

Hishammuddin Hussein, Malaysia's transport minister, told Chinese TV: Hishammuddin Hussein, Malaysia's transport minister, said it was unfair for all of the blame to focus on the Malaysian response to the crisis. "Just putting MAS [Malaysia Airlines] on the witness stand [is not enough]," he told Chinese TV. "We also need to bear in mind what is the role and responsibility of Rolls-Royce, of Boeing, of all these expert agencies. Where is their voice?"