Wiktionary
fair wind
n. (context nautical English) A wind blowing in the direction the sailor wants to go, ie. favourably. (Reference: http://en.wikipedia.org/wiki/Ray%20Parkin, ''H. M. Bark Endeavour'', http://en.wikipedia.org/wiki/Miegunyah%20Press, second edition 2003, ISBN 0-522-85093-6, page 210.)