The graphic below is convincing that the navy used a sound analytical approach at the time in 1937 and that much ground (and sea...) was covered.
I covered this in great detail in Finding Amelia.
When I look at the graphic I am appalled that so little time and so few assets were dedicated to searching the islands of the Phoenix Group given the volume of evidence the Navy had indicating that Earhart and Noonan were there and had been calling for help. To me, the crucial failure occurred on July 10 when Capt. Friedell (
USS Colorado) sent the following message to Admiral Murfin who was directing the search from Pearl Harbor:
“With completion [of] flight this afternoon, all islands Phoenix Group have been located and carefully searched for any sign of Earhart plane or inhabitants with exception Winslow reef and reef and sandbank to the northward. The charted position of these places and for several miles in vicinity was covered twice without locating them.”
The logic seemed to go:
• the post-loss radio signals indicated that the plane must be on land somewhere in the Phoenix Group
• Colorado has carefully searched all islands of the Phoenix Group and found no sign of the Earhart plane or inhabitants
• Therefore, all of the post-loss radio signals must have been bogus
At that point, Colorado was released, Lexington took over, and the rest of the search was conducted in areas based entirely upon speculation and supposition. The post-loss signals had stopped before Colorado began searching the Phoenix Group and nobody seems to have considered the possibility that the plane may have been washed off a reef or hidden in dense vegetation. On the voyage out from California, Lexington had drawn up a plan for sweeping vast stretches of open ocean with its aircraft. Friedell's claim that the Phoenix Group could be eliminated opened the door for that plan to be put in operation - which is exactly what happened.