"A harrowing 12 months of uncertainty and sorrow" - that is how Australia's prime minister described the suffering of the families of passengers and crew lost aboard flight MH370.
In the parliament in Canberra, Tony Abbott told relatives: "We are taking every reasonable step to bring your uncertainty to an end." But he hinted that if the present phase of the hunt for the missing Malaysia Airlines jet proves fruitless, it may be scaled back. "I cannot promise that the search will go on at this intensity forever," he said.
It is exactly one year since 227 passengers - 152 of them Chinese citizens - checked in for a routine departure from Kuala Lumpur, destination Beijing. Twelve crew were assigned to the flight, which was to depart shortly after midnight on March 8.
Four passengers failed to check in, while two of the people who did fly were Iranian nationals travelling on stolen passports.
The last contact with the Boeing 777 MH370 took place at 1.19am, local time, when the captain signed off from Malaysian air-traffic controllers with the words "Goodnight Malaysian three seven zero". It took a further six hours before the airline told the world that one of its aircraft was missing. Initially, the jet was assumed to have crashed in the South China Sea towards the southern tip of Vietnam.
Yet ground-breaking analysis of fragmentary "pings" picked up by Inmarsat showed that the plane was still flying at the time the loss was announced. It was deduced to be flying along one of two corridors: north-west across southern China and Central Asia towards the Caspian Sea, or south across the Indian Ocean to the west of Australia. With no sightings of the aircraft on land, the plane is presumed to be in the sea off Australia. Yet after months of a multinational hunt costing tens of millions, not a single trace of the jet has been found. For the grieving families, the heartbreak continues.
The Australian Transport Safety Bureau (ATSB) began the current phase in September. The search area where the plane is deemed most likely to be has been narrowed down to a patch of previously unmapped sea three times the size of Wales. The zone is in the Roaring Forties, one of the planet's roughest stretches of ocean.
Four specialist vessels are inspecting the seabed by sonar, with three classifications for unusual features. Class 3 for contacts that are of some interest as they stand out from their surroundings but have low probability of being significant; about 100 have been identified. Class 2 sonar contacts are typical of man-made objects, but not resembling an aircraft debris field; about a dozen have been found; Class 1 contacts "are of high interest and warrant immediate further investigation"; none has yet been identified.
Not according to Martin Dolan, the bureau's chief commissioner. At the start of the current phase last September, he told me he was fairly confident of finding the plane within 12 months: "A year is a rough estimate based on the capabilities of the vessels we have, the nature of the sea floor and the extent of the higher probability areas. We expect to find the aircraft in the course of that search, but there is no complete guarantee of success."
Anything that helps the relatives find closure is clearly valuable - but is that the only purpose of the search?
No. Finding MH370 is critical to help the airline industry to devise systems that will prevent any repeat of the tragedy.
Some say that the only theory that fits all the known facts is that this was a bizarre suicide mission by the captain. Is that credible?
Certainly it is accepted that someone was at the controls when the aircraft's transponder was switched off, causing the aircraft to become almost invisible, and that changes of course were commanded.
Captain Zaharie Shah and first officer Fariq Abdul Hamid, below, are plausible candidates because they worked on the flight deck and had all the professional knowledge.
The first book on the tragedy, 'Goodnight Malaysian 370', postulated that the captain chose his moment perfectly: just after signing off from Malaysian air-traffic controllers, in aviation "no man's land" in the middle of the South China Sea, he locked his co-pilot out of the cockpit. Then, it is presumed, he depressurised the cabin to incapacitate - and quickly kill - the other passengers and crew.
He then, the theory goes, set the controls for a patch of the planet where the aircraft would never be found - even taking the trouble to execute a landing on water gentle enough to keep the plane intact.
This grisly version of events has plenty of supporters. One senior UK aviation figure says: "Whether he let the aircraft run out of fuel or deliberately crashed it into the sea we will never know, but my guess is it was dived deliberately at the chosen spot."
But the theory also has some inconvenient puzzles. Suppose the co-pilot had indeed been locked out of the cockpit. Immediately he, other crew and passengers would try to communicate with the outside world using mobile phones.
Since the aircraft promptly flew back across Malaysia, it seems likely that at least some attempts should have succeeded.
To date none has been identified.
(© Independent News service)