[alancalverd (OP)]

Due to a minor navigational error, ace pilot Alan has run out of fuel in the Sahara instead of landing in Dublin (180°, 280° - anyone can make a mistake). Fortunately he has some water and has finally worked out how to locate himself with the GPS.

What is his best strategy for survival if he is (a) 20 (b) 100 (c) 300 miles from the nearest town and has (i) 5 liters (ii) 20 liters or (iii) 100 liters of water?

You may assume that he is, of course, athletically fit and has a reasonable number of Mars bars or non-melting equivalent, or that he is prepared to eat his dead passenger. 

[Bored chemist]

In almost any such circumstance, his best bet is to stay with the plane.
Planes are big enough to see from another (search + rescue) plane; people aren't.

If he is 300 miles from town and has 5 litres of water his best bet is probably to hide from the sun under the plane.
At least that way they will find his body- which will be some comfort to his grieving relatives..

[jeffreyH]

Hmmmm ... The old stay with the plane scenario.

[chris]

This puts me in mind of this wonderful Question of the Week from a few years back:
https://www.thenakedscientists.com/forum/index.php?topic=13669.0

Transcript and audio here: https://www.thenakedscientists.com/articles/questions/drink-wine-or-drink-nothing