Rescuers have an arduous task in scouring the ocean as they try to locate the Boeing 777. Why?

How hard can it be to find a 200,000 kg-weighing, high-tech, multi-radar-enabled 21st century aircraft? Over these traumatic and anxiety-ridden past seven days, we have discovered that it can be disturbingly simple for a highly trained pilot with ill intentions to make an airplane disappear into thin air.

On Saturday, investigators said it was all but "conclusive" that Flight 370 had been hijacked by a trained and highly skilled pilot. Around 40 minutes after Malaysia Airlines Flight 370 took off from Kuala Lumpur at 12.40 am local time, bound for Beijing with 239 people on board, the airplane made its last contact with civilian air traffic control, at 1.21 am. The plane then vanished, sparking a massive, multi-national search operation over the Gulf of Thailand, where it last made contact contact.

Initial suspicions were the aircraft may have had a disastrous mechanical failure at 35,000 feet, prompting a shutdown of all communications and control. But searches in the area over the past week yielded not a single piece of debris.

It then emerged in the middle of last week that all was not what it seemed with Flight 370. Malaysian military radars picked up an aircraft at 2.40 am, more than an hour later, at a location hundreds of kilometers west of the Gulf of Thailand. (This begs the frustrating question: were dozens of vessels and aircraft from more than half a dozen countries expending their resources searching in the wrong location for five crucial days, because Malaysian authorities haven't been entirely forthcoming with their information? As of Friday, China said seven of its eight deployed vessels were still scouring the Gulf of Thailand.) On Friday, however, investigations all but ruled out a mechanical failure at 1.21 am, when military radars revealed that the Boeing 777 had been deliberately flown off-course.

I spoke to Captain Mohan Ranganathan, a veteran pilot and instructor with 20,000 hours flying experience who as a pilot with Silk Air frequently flew in the region, to make sense of the latest developments. Ranganathan has also worked on investigations into accidents, and is a well-known expert on international Approach and Landing Accident Reduction (ALAR) programmes.

He had three interesting points to make. First, the course charted showed the Boeing was almost certainly in the hands of a veteran pilot, someone among the 239 people on board who had possibly flown these routes before. As I reported today, the last navigational way point - a geographic reference for pilots - tracked by Malaysian military radars, called IGREX, was south of the Andaman Islands.

The Boeing 777 charted a careful, zig-zag course to IGREX from the point where it lost contact with air traffic control over the Gulf of Thailand. That point, called IGARI, was reached by the Boeing at 1.21 am local time on Saturday, an hour after take-off from Kuala Lumpur. At that same time, the transponders of the aircraft stopped communicating with air traffic control, suggesting they may have been manually disconnected.

Reuters quoted Malaysian military officials as saying the Boeing then abruptly turned west to another well-known waypoint, VAMPI, northeast of Indonesia. It then turned north to the waypoint GIVAL, south of Phuket. It then sharply turned northeast to the waypoint IGREX, which is just south of the Andamans and along the route to Port Blair. That was the last point of tracking by Malaysian military officials.

I asked Ranganathan how the aircraft could have come so close to India's military radars in the Andamans and avoid detection. There are at least three possible explanations. One, it crashed into the Andaman Sea, where India, the U.S. and other countries are still searching for debris. Two, as Manu Pubby reports in today's Indian Express, the radars were -- amazingly -- not always left on, a scenario that leads to even more disturbing questions about our national security.

A third outcome is that perhaps our radars had no reason to suspect the aircraft. This is possible, Ranganathan said, if someone had filed a fictitious flight plan at, say, Medan in Indonesia for a flight - under a different name - to perhaps a destination in the Indian Ocean. This would suggest a long thought-out plan to take control of the aircraft and fly it to a third destination, as U.S. officials suspected this week, for some "later purpose". Only investigations will tell us if such a plan was successful, or if the aircraft plunged into the waters of the Indian Ocean en route.

The plane, we know now from reports in the Wall Street Journal, flew for four or five hours after 1.21 am, going by "pings" received from satellite links that are active even if transponders are manually disconnected, which explains the disappearance over the Gulf of Thailand from civilian radars. Ranganathan said it is possible to even disable the satellite link, as circuit breakers are in the cockpit. Doing so, he said, would require "somebody who knows the aircraft like the back of his hand".

On Saturday morning, Malaysian officials suggested the line of investigation was disturbingly proceeding in that direction, as close to a hundred ships and vessels from a dozen countries continued an even wider search, across vast swathes of the Indian Ocean where Flight 370 could have been taken by the rogue pilot. The plane had enough fuel, flying at 30,000 feet, to cross the Arabian Sea and even reach the western coast of Africa or even waters off Australia, Ranganathan pointed out.

The Malaysian Prime Minister in a statement to the media said Saturday the search in the Gulf of Thailand and the South China Sea had been abandoned, and operations were taking place in an expanded area further west, in two corridors: one running from Thailand all the way north to the Kazakhstan-Turkmenistan border, and the second southwards deep into the southern Indian Ocean.

This leaves rescuers an arduous task in scouring the ocean as they try to locate the Boeing, even as hope, a week on, fades to despair for the relatives and friends of the 239 women and men on board Flight 370.