The 16-strong team will sail from Fiji on July 13 and are scheduled to anchor outside the island's coral reef around July 18. The contingent includes a representative of the government of Kiribati, which has registered the remote Nikumaroro and surrounding islands as the Phoenix Islands Protected Area and introduced a range of environmental regulations. The team will have 17 days on the island to fit archaeological facts with the hypothesis.

Since July 2, 1937, when Earhart and Fred Noonan, her navigator, disappeared over the Pacific on her second attempt to circle the globe close to the equator, there have been dozens of theories as to what happened after they took off from Lae, New Guinea.

For many years, the accepted wisdom was that their Lockheed Model 10E Special 'Electra' had simply run out of fuel and crashed into the ocean as they searched for Howland Island, their final refuelling stop before flying to Honolulu and completing the journey by touching down in Oakland, California. Even Gillespie himself thought that was the most likely explanation, until it was pointed out that even without the benefit of modern navigational technology, Earhart and Noonan did have the equipment to make it to dry land.

According to Tighar's theory, 20 hours and 13 minutes into the flight - and with less than four hours of fuel left - Earhart and Noonan were unable to make visual or radio contact with Howland Island. They implemented the only procedure open to them that would minimise the chance of having to ditch at sea, proceeding southeast on a heading of 157 degrees, a supposition backed up by the last radio message received from the Electra, when Earhart said she was flying on a 157/337 navigational line of position.

They believe Earhart landed the plane on the reef flats of uninhabited Gardner Island, as Nikumaroro was then known, just north of the wreck of the SS Norwich City. Supporting evidence in Tighar's file includes interviews with residents who colonised the islands in 1938 and report seeing a wrecked aircraft on the reef, long before the possibility of any second world war activity, and photographic evidence that has only recently confirmed the presence of anomalous material on the reef as early as October 1937.

The evening of Earhart's disappearance, the aircraft's radio was used to transmit distress calls. The signals were heard by the searching US Coast Guard vessel Itasca on 6,210 kilocycles, the frequency Earhart said she was switching to in an earlier transmission.

A radio station on Nauru also reported 'fairly strong signals, speech not intelligible, no hum of plane in background, but voice similar to that emitted from plane in flight last night'.

For the aircraft to be sending signals, it had to be on land and able to operate the generator-equipped engine to recharge its batteries. Over the next few days, further transmissions were heard. Tigar theorises that as the search continued, rougher seas and increased surf forced Earhart and Noonan to abandon the aircraft, which was washed off the reef and sank. They sheltered in the bush, but when search planes from the USS Colorado were heard overhead on July 9, Earhart and Noonan were unable to reach the open beach in time to be seen.

Literally marooned on a desert island, Earhart and Noonan survived for a time, but eventually would have succumbed to infection, food poisoning or simply thirst. They suggest Noonan died not far from the site of their landing. Earhart died at a makeshift camp near the shore of the lagoon on the southeast of the island.

These theories are supported by the extensive British government records - which only came to light in 1987 - confirming the discovery in 1940 of the partial skeleton of a castaway who perished before the island was settled in 1939. With the bones were found a sextant box and the remains of a man's shoe and a woman's shoe.

The conclusion to Tighar's scenario is that the aircraft was destroyed by surf action and during the years the island was inhabited, between 1938 and 1963, colonists recovered and used bits of wreckage; an aircraft control cable was apparently used as a fishing line and a large fishing hook was fashioned from aluminium in 1944. The locals report that the material came from 'an airplane that was here when our people first came'.

The six expeditions to Nikumaroro to date have turned up more shoe fragments that have been dated to the 1930s, sheets of aircraft skin, lengths of aircraft cable and shards of Plexiglass that exactly match the curvature, material and thickness of the window in the Electra's fuselage.

'Our hope is that we can find enough new evidence on this trip to make it possible to raise the money to do a thorough deep water search off the west end of the island, where we think the wreckage of the plane is,' said Gillespie, who is also the author of Finding Amelia: The True Story of the Earhart Disappearance. 'We'll have better surveying and mapping technology on this trip, but there is no magic Amelia-finder. Most of what we'll be doing is conventional down-and-dirty archaeology.'

And much of the responsibility for that will be down to the senior archaeologist on the trip, Dr Tom King. 'At the Carpenter's House and vicinity, our main target in the village, we'll initially clear the site and then sweep it with metal detectors, plotting hits,' Dr King said. 'Based on this search and what we can see on the surface, we will lay out a pattern of squares to be excavated, each probably a metre on a side. Excavated soil will be put through 1/4 inch screen and we'll record everything we find, but take away for analysis only stuff that looks relevant to our research.'

At the site where the settlers are believed to have buried the human skull they found. 'Our main jobs are to further excavate 'the hole' and to very carefully search the slope of the surge ridge above it, down which the cranium may have rolled, shedding teeth,' he said.

'One specific location of interest is a fire feature with brown glass shards, found late in the 2001 project but not excavated,' he added. Debris from the hole will be screened and then scanned with ultraviolet light, in which teeth ought to glow blue, Mr King said. 'We know that the cranium had no teeth in it when it was dug up by the island's administrator in 1940. If it had teeth when it was buried, they ought to still be in the hole.

'Anything that looks like a tooth, a bone, or anything else that might retain DNA must not be touched with bare hands,' he said. 'We'll have latex gloves on site for recovering such items, into clean ziplock bags.'

The work will be exhaustive and exhausting, Mr Gillespie and Mr King know from first-hand experience. And it may still not turn up the vital, conclusive item that their critics will finally accept as proof that Earhart died on Nikumaroro. But for others, the search for the famed flier is a treasure hunt; for Mr Gillespie and Mr King it is a process that will one day answer at least some of the questions that remain unanswered after she took off into the blue 70 years ago.