Sentence:  Down at the end of the field when ready for the take-off, I'd taxi the ship off the <WSD>runway</WSD> and tell him why I did that—"so as not to block incoming ships," and I'd tell him at the same time why the incoming ship was supposed to land in the first third of the field and why in the take-off we were going all the way to the end of the <WSD>runway</WSD> and not try to take off up the middle of the <WSD>runway</WSD>. 
Meaning of the word marked with <WSD> tags:  A section of land, usually paved, for airplanes to land on or take off from.