Investigators have detailed the effort to locate Malaysia Airlines flight MH370 in the initial four hours after its disappearance, but the preliminary inquiry report gives little information that had not previously been disclosed.

The Malaysian transport ministry has clarified that the aircraft passed the IGARI waypoint just after 01:21 local time on 8 March but that its radar data label vanished just 9s later.

Ho Chi Minh air traffic control centre, which had been expecting to take responsibility for the aircraft at this time, first inquired as to the whereabouts of the Boeing 777 at 01:38.

It was told that, after passing IGARI, the aircraft had not returned to the Kuala Lumpur radio frequency, having been instructed to call Ho Chi Minh centre on 120.9MHz.

Ho Chi Minh stated that radar contact was established over IGARI, but there had been no verbal contact, and that the radar track disappeared in the vicinity of the BITOD waypoint.

“Attempts on many frequencies and aircraft in the vicinity received no response from MH370,” reads a summary of the actions taken after Ho Chi Minh controllers formally reported no contact with the aircraft.

Over the next 15-20min controllers sought to clarify whether the aircraft was flying in the Phnom Penh flight information region – part of Cambodian airspace – based on information from the airline.

But the flight plan only involved routing through Vietnamese airspace, and there had been no contact with Cambodian controllers from MH370.

Based on a signal at 02:33, according to the summary, Malaysia Airlines’ operations centre told Kuala Lumpur controllers that MH370 was in “normal condition” and gave co-ordinates in the region of the Vietnamese east coast.

Ho Chi Minh centre asked the crew of another Malaysia Airlines aircraft, the Shanghai-bound flight MH386, to try to reach MH370 on Kuala Lumpur’s frequency, and the crew was separately requested by Kuala Lumpur to try the emergency frequencies as well.

Over a 2h period from 03:30, until the Kuala Lumpur rescue co-ordination centre was activated at 05:30, controllers checked whether the aircraft had made contact with Hainan, Hong Kong, Beijing or Singapore.

The preliminary inquiry states that military radar tracks – indicating the possibility that MH370 turned back and overflew the Malay peninsula – were being examined as early as 08:30, just 3h after the co-ordination centre was put into operation.

“The aircraft was categorised as friendly by the radar operator and therefore no further action was taken at the time,” says acting transport minister Hishammuddin Hussein, explaining the absence of a military response.

This prompted an order to two Malaysian naval vessels in the Malacca Strait – and subsequently a military aircraft – to begin a search and rescue operation.

Updated projections on MH370’s flight path suggest that around 02:27, about 5min after the last trace by military primary radar, the 777 turned south, passing over Pulau We island off the northern tip of Sumatra.

No trace of the twin-engined jet, or its 239 occupants, has been found since despite an extensive search in the southern Indian Ocean.

Malaysia’s preliminary inquiry report puts the highest confidence in a flight track based on a speed of 323kt, while a mid-probability projection is founded on a faster 350kt profile. Speeds between these endpoints are considered to be the least likely.

Its sole recommendation requests that ICAO examines the safety benefits achievable from real-time tracking of commercial aircraft.

Source: Cirium Dashboard