I would like to add some aviator thoughts to this thread not to debunk any other theory but perhaps to help others understand why I think an island SSE of Howland was the most likely end point. Pick one...doesn't have to be Gardner. But it is important to know how aviators think about navigation and their decision processes. It is an adjustment of my own experience with some added historical perspective of reading about how pioneers like FN developed the early modes of over-water navigation that made it possible for WW2 aviators, even single seat pilots, to successfully navigate over vast open water. George Bush would know these techniques.
First, point of no return. You always know it and you always compute it. FN would have known his PONR for New Britain and there is no reason for them to think they would not find Howland until they got to the extended LOP and didn't find it. They would not have turned around early as they had no reason to believe they wouldn't find it. Hence turning around for NB would have been out of the question for him. Perhaps the
Bonins Gilberts but, interesting enough this is an island chain roughly on a 337/157 hence turning around to go there would mean one chance as you are flying perpendicular to the chain. If you missed an island you missed them all (better to fly along a chain than perpendicular to one). Next nearest past
Bonins Gilberts is Nauru and easy to miss. Again, you know you are on an extended LOP of 157/337 but you do not know where N/S so you could miss things you turn around to go to either N or S. Past that you are landing in water. He probably also knew his PONR to Nauru and had exceeded it.
The other point is what do I do when I get to extended LOP and do not find Howland? I assume I missed N or S. So I fly NNW (337) a little ways to see if I find it (or Baker) but not too far as there is nothing else beyond in that direction. Then You turn SSE (157) assuming you missed to the N. This is a good direction because you chance finding, in sequence, Howland, Baker, Mackean, Kanton or Gradner, Tokelau, and eventually American Somoa although I think even FN knew he didn't have the fuel to make it there. So you expend a little fuel looking for Howland on 337 but not long, as you are on reserve, and you give the greatest time to 157. If you turn around 180 you have one slight chance at
Bonins Gilberts and a infinitesimal chance at Nauru. FN had been doing this for a while. As I said in an earlier post, a good aviator doesn't get that way without learning to have contingency plans. In 1937 they didn't live very long if they didn't. FN would have already figured this out before takeoff. So when he got to extended LOP he told AE "turn left to 337". He would have allowed her just enough time to make sure they did not find Baker or Howland N of them and then said "turn to 157". That is the only heading that it makes sense to fly on till you run out of gas...not E, not W.
My two cents for what its worth and I will not abandon that as a preferred answer even if nothing is fund on this expedition. Because they could have missed all those island too and landed in the water...but on a 157 heading.
Interesting about underwater topography in S Pacific. All the islands/atolls are essential Mt peaks. Where there is extensive gradual rise to an island the change in water color from deep blue to light blue is the first thing you see, not the island itself. In S Pacific there isn't that distinct change. It goes from Deep Blue to reef in a few hundred feet. I flew into Midway Island one night on a C-141 going to pickup a broke F-16 there. W/O the rotating beacon you never would have sen it. Later I flew that single engine airplane all the way back to Oahu unrefueled. I thanked the Lord for GPS as I tried to locate each one of Tom Hank's tiny little islands along the way to castaway on in case my one motor quit. It was very challenging from ~30K feet much less at 1000-8000 feet. And I knew exactly where I was all the time. My hat's off to FN for even getting in that airplane that day to try to find an island smaller than Midway.
JB
PS, sorry brain freeze, was thinking Tarawa, which for me means Betio, and somehow Bonins jumped out as i was rapidly typing. Obviously meant Gilberts...sorry.

If they could have made Bonins they could have flown on to Hawaii.
