Flight Of Fancy Meaning

(idiomatic) An idea, narrative, suggestion, etc. which is extremely imaginative and which appears to be entirely unrealistic, untrue, or impractical; thinking which is very speculative.

Example: 1704, Jonathan Swift, A Tale of a Tub, section 8,
  Whereas the mind of man, when he gives the spur and bridle to his thoughts, does never stop, but naturally sallies out into both extremes of high and low, of good and evil, his first flight of fancy commonly transports him to ideas of what is most perfect, finished, and exalted.
1848, Charles Dickens, The Haunted Man and the Ghost's Bargain, ch. 1,
  Who might not, by a very easy flight of fancy, have believed that everything about him took this haunted tone, and that he lived on haunted ground?
1939, "Canadian Secrecy," Time, 20 Nov.,
  No German troops were mobilized along Canada's border last week, no Canadian cities had been bombed, and only by the remotest flight of fancy could alarmists see the Dominion as a battleground.