Three minutes. That is the time frame to deliberately switch off a plane's transponder and remain invisible on radar without arousing any suspicion if they are flying between Malaysian and Vietnamese airspace, pilots say.
One pilot familiar with the route said there is a point over the Igari navigational waypoint in the South China Sea where commercial pilots have to use radio to communicate with air traffic controllers as the planes would be out of reach of civilian radars.
Malaysia Airlines Flight MH370 carrying 239 people on board disappeared over the Igari area last Saturday while en route to Beijing. It never arrived and there has been no trace of the aircraft since it vanished seven days ago.
"There is three-minute window to do this, and the transponder can only be switched off manually," the pilot told The Malaysian Insider on condition of anonymity.
He said that the transponder carried all information about the aircraft's identity or Ident, altitude, location and other data that air traffic controllers need to ensure planes fly on dedicated corridors.
"Once the transponder is off, a plane is only a blip with no information for civilian radars," he added, saying military primary radars are not privy to such data.
ABC News had reported that United States officials believe two communications systems on the missing Malaysia Airlines flight MH370 occurred separately, indicating that it may have been a deliberate act, although other American officials said the Boeing 777-200ER had sent data for another four hours after vanishing from radar screens.
According to the report, two US officials said that they believe the data reporting system was shut down at 1.07am, while the transponder was shut down at 1.21am on Saturday, when the flight carrying 239 people vanished from radar screens.
But other officials had said the aircraft continued transmitting data for at least four more hours after vanishing from radar screens, with its last ping over water.
"This indicates that it may well have been a deliberate act," ABC news aviation consultant John Nance reportedly said about the communication shutdown.
The report said the US team is convinced that there was manual intervention, and that it was likely not an accident or malfunction that caused the plane to go missing from the sky.
It was also reported that satellites picked up faint electronic pulses from the Beijing-bound flight after it went missing on Saturday, but the signals gave no information about where the stray jet was heading.
The United States, which is part of an international search for the missing jetliner, had also said that the search area may soon expand into the Indian Ocean, consistent with the theory that the plane may have detoured to the west about an hour after take-off from Kuala Lumpur.
From data supplied by Malaysian authorities, the US believes missing flight MH370 was flying for another four hours after contact was lost with it.
Contact is usually maintained through the Aircraft Communications Addressing & Reporting System, or Acars, which allows the plane to maintain contact with ground stations via radio or satellite.
The unaccountable four hours of possible flying time necessitated the search and rescue operations to expand their coverage to cover the Indian Ocean, too.
As such, the US was moving the USS Kidd destroyer northwest through the Strait of Malacca towards the Indian Ocean, to an area recently searched by US surveillance aircraft, P-3C Orion, which can cover up to 3,800 square kilometres every hour.
But Malaysia has knocked down the theory that the plane may have flown four or five hours after disappearing from radar, saying both Malaysian Airlines and Rolls-Royce have said that the bursts of engine data ended at 1.07am on Saturday, some 20 minutes before it vanished from civilian radar systems.
Dismissing the report as inaccurate, acting Transport Minister Datuk Seri Hishammuddin Hussein said yesterday that the last data transmission from the jetliner was at 1.07am.
"Rolls-Royce and Boeing teams are here in Kuala Lumpur and have worked with MAS and investigation teams since Sunday. These issues have never been raised," he reportedly said.
It was reported in the Washington Post today that evidence that MH370 flew on for another four hours after vanishing early Saturday came from data shared by Malaysian authorities, not from engine maker Rolls-Royce. – March 14, 2014.