SEPANG: MAS Airlines flight MH370 dropped to an altitude of 5,000 feet, or possibly lower, to defeat commercial (secondary) radar coverage after it turned back from its Kuala Lumpur-Beijing route on March 8.
Investigators are poring over the Boeing 777-200ER's flight profile to determine if it had flown low and used "terrain masking" during most of the eight hours it was missing from the radar coverage of possibly at least three countries.
Top officials, who make up the technical team that had been holed up from morning till late at night here, are looking at the possibility that the jetliner, carrying 239 people, had taken advantage of the busy airways over the Bay of Bengal. By sticking to commercial routes, the flight may not have raised the suspicion of those manning primary (military) radars of the nations it overflew. To them, MH370 would appear to be just another commercial aircraft on its way to its destination.
"The person who had control over the aircraft has a solid knowledge of avionics and navigation, and left a clean track. It passed low over Kelantan, that was true," said officials.
"It's possible that the aircraft had hugged the terrain in some areas, that are mountainous to avoid radar detection."
This technique is called terrain masking and is used by military pilots to fly to their targets stealthily, using the topography to mask their approach from prying microwaves. This type of flying is considered very dangerous, especially in low-light conditions and spatial disorientation, and airsickness could easily set in. The stresses and loads it puts on the airframe, especially an airliner of the 777's size, are tremendous.
"While the ongoing search is divided into two massive areas, the data that the investigating team is collating is leading us more towards the north," sources said.
Prime Minister Datuk Seri Najib Razak said the flight data showed that the plane's last communication with the satellite, reported as Inmarsat, was in one of two possible corridors: a northern corridor, stretching approximately from the border of Kazakhstan and Turkmenistan to northern Thailand; or a southern corridor, stretching roughly from Indonesia to the southern Indian Ocean.
Sources close to the investigation by a multinational team told the New Straits Times that the probe would also focus on regions with disused airports equipped with long runways capable of handling "heavies" like the Triple Seven. If anything, the area investigators could be covering has been narrowed down to MH370's eight hours of flight time, based on the jet's fuel load.
This followed MAS' confirmation of records that showed that the pilot had not made any amendments to the plane's fuel requirements. It was enough to take it to Beijing, with a 45-minute reserve in case of diversion to an alternate field.
Investigators are also factoring in the extra fuel the aircraft would have burnt in the denser lower air if it had flown "down on the deck" for sustained periods. Pilots agree that MH370 would lose up to about two hours of fuel. Any erratic manoeuvres would have also eaten into the jet's fuel reserves.
"Going by the hijacking theory, assuming it had landed, where would one hide a Boeing 777?" one said.
From about the time the aircraft made the turnback at waypoint Igari near the Vietnamese airspace, right up to the point where it left military primary radar coverage, six routine automated signals from the aircraft (known as electronic handshakes or "pings") were registered on the Inmarsat satellite network.
The last confirmed handshake was at 8.11am on Saturday, which would indicate that the aircraft continued flying for nearly seven hours after contact was lost.
Sources also confirmed that the seventh handshake never came.
"The seventh signal was sent but there has been no feedback.
"There are two likely possibilities -- either the plane landed somewhere and the engine was shut down or it crashed."
Kuala Lumpur has officially approached countries, in hopes that they would openly share and review their radar and satellite data.
It has not gone unnoticed that crucial information had been leaked and appearing in the foreign media, quoting their respective governments' sources. Such information, crucial to the search for the airplane, only came the Malaysian government's way later.
Investigators are also calculating to determine how far the aircraft may have flown and the possible landing sites.
"As soon as the first country comes up with evidence of the flight's position after its last confirmed position (320km northwest of Penang), we will be able to refine the search and better determine its possible location."
Data harvested from Inmarsat was not able to do that as the static satellite could only detect the pings at a 40o angle.
Meanwhile, another highly-placed source told the NST that initial forensics checks on Captain Zaharie Ahmad Shah's flight simulator showed that it was "clean".
However, experts are probing deeper into the footprint of the homemade simulator, which he had at his home in Shah Alam.
The same source said investigators who had opened investigation papers into the case was looking at all the passengers' backgrounds.
"The police, among others, are establishing their background and recent contacts.
"They are not leaving anything to chance and are even checking if any one of them had taken up any insurance policies recently."
A source with Malaysia Airlines, meanwhile, confirmed that both pilots were on that plane as rostered.
They had not swapped flight schedules with anyone. MAS pilots get their rosters at the end of every month.
Foreign media reports quoting a source familiar with US assessments of Inmarsat "pings" said it looked like the plane turned south over the Indian Ocean, where it would presumably have run out of fuel and crashed.
"So, its location will be extremely difficult to pinpoint.
"Without further radar/satellite/eyewitness testimony, say experts, it is very much like looking for a needle in a haystack," the reports said.
Additional reporting by Aliza Shah and Tharanya Arumugam