THE crew of an Australian air force P3 Orion spy plane reported that bad weather hampered its search for boats carrying asylum-seekers on the day a vessel sank, drowning 353 men, women and children.

The crew admitted the setback to superiors after the plane flew low off the Indonesian coast on the morning of October 19, only hours before the boat dubbed Siev X capsized in the area.

The P3's official post-flight report concluded that bad weather had given the plane a lower-than-usual "75 per cent probability of detection" of all boats in the key search zone called "Charlie Northwest", where Siev X is likely to have sunk.

On that flight, the crew detected by radar and visual sighting 22 fishing vessels and eight merchant ships in its patrol zone - but not the ill-fated Siev X.

The P3 also detected seven ships in nearby Indonesian waters, but could not visually identify them. Despite this gap in surveillance caused by the weather, the navy, which directed the surveillance operations, did not order another P3 into "Charlie Northwest" until the following day, October 20.

The Weekend Australian has revealed that on the morning of October 20 - as survivors still clung to the wreckage of Siev X - a P3 flight passed over the area but, not knowing of the tragedy, did not spot any survivors.

The Australian Government will provide a Senate committee with full details of its surveillance of the waters between Indonesia and Christmas Island at the time of the Siev X tragedy.

The Government hopes that evidence will debunk claims the navy turned a blind eye to the fate of the Siev X and its human cargo.

The navy has been on the defensive over the Siev X tragedy after it was revealed last month that it received a spate of intelligence reports that the boat had departed Indonesia for Christmas Island and was dangerously overloaded.

The navy has admitted it dismissed this intelligence as inconclusive, and chose not to step up its routine daily surveillance of the area to search specifically for the SIEV X.

Prime Minister John Howard has described as "outrageous" suggestions that the navy did not do all it could to prevent the SIEV X tragedy.

Defence sources yesterday said the P3 planes that failed to spot the SIEV X sinking and its aftermath on October 19 and 20 flew between 1000 and 1500 feet.

SIEV X sank in the vicinity of Charlie Northwest on the afternoon of October 19, five hours after the P3 patrol left the area.

At least 44 of the survivors were still alive in the water the following morning, October 20, when another P3 flight came through the area.

On the same morning the navy received a detailed intelligence report - the second in two days - that SIEV X had left Indonesia for Christmas Island. The report added that SIEV X was grossly overcrowded with up to 400 people aboard.

The new navy chief Rear Admiral Chris Ritchie told a Senate committee last month that there was no reason to change the navy's surveillance pattern to search for SIEV X.