flown by the seat of one's pants

Verb

fly by the seat of one's pants (third-person singular simple present flies by the seat of one's pants, present participle flying by the seat of one's pants, simple past flew by the seat of one's pants, past participle flown by the seat of one's pants)

1. (idiomatic) To pilot an aircraft without the aid of instruments and without a flight plan, using only instinct, visual observation, and practical judgment.
   • Between world wars, when Douglas Bader was a cocky, teen-age R.A.F. cadet . . . a man could navigate by eye and the nearest railroad track and fly by the seat of his pants.1955 February 21, “Planes for Pleasure”, in Time
2. (broadly, idiomatic) To use one's judgment, initiative, and perceptions as events unfold in order to improvise a course of action without a predetermined plan or without the desirable data inputs to decision making.
   • “Unlike Obama and his methodical process, McCain was flying by the seat of his pants,” the authors observe.2010 January 14, Jacob Heilbrunn, “Election Confidential”, in New York Times, retrieved 25 Jun 2011

   Synonyms:

   play by ear, make it up as one goes along, wing it