NavList:

My rather late comments on this thread are fourfold. 
1.  Re the ‘timeline’ business:  Articles upon this, whether learned or precis of precis, spend too much time looking at Earhart and too little looking at Noonan.  Noonan’s history at sea and in the air goes back initially to years before the mast in a square rigger.  (viewable in Glasgow UK by the way).  He had crossed the Pacific many times as navigator both as a ship’s officer and on proving flights with Pan-AM.  Whilst it might have been possible for Earhart, because of her relative inexperience to become confused over this, for Noonan it would have been impossible.

2.  The navigation for the flight was essentially celestial monitored manual dead reckoning with the possibility of radio back bearings at the start and the hope of radio bearings at the finish.  If I recall from Nav-School, the errors in manual dead reckoning navigation are pilot error (i.e. inability to exactly follow the required heading), compass error, TAS error, and wind error.  Given that a one-degree error in either of the first two leads to one mile in sixty across track error and this flight was 2,200nm only celestial monitoring could have prevented a considerable error building up.  Heading appears a lot in these discussions.  Celestial monitoring comprises not just celestial fixes and single position lines but also celestial heading checks.  The aircraft certainly carried a sextant, probably bubble, but not a peri-sextant, so there could have been no 'free' heading check with each sextant shot.  Therefore, perhaps someone can tell me if the aircraft carried an astro-compass, or at least a hand-bearing-compass to check compass heading?

3.  Post and Gatty, and then Post solo, flew much further north avoiding most of the Pacific altogether.  Did Earhart ever consider this as a possibility?

4.  Not enough consideration is given to the low vertical extent of Howland Island.  Its maximum height is 3M (10ft).  Francis Chichester flying much shorter distances but solo in a less stable aircraft had the advantage of trying to find islands of 319M(1047ft) and 875M (2871ft) maximum height.  Earhart and Noonan were effectively trying to find a needle in a haystack.  When their hoped-for radio final guidance didn’t manifest itself, their chances of success must have been near zero.  The error, if there ever was one, occurred not during the flight but at the initial planning stage in leaving themselves such a problematic Pacific crossing.  DaveP