CFR > Title 14 - Aeronautics and Space > CHAPTER I—FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION > SUBCHAPTER F—AIR TRAFFIC AND GENERAL OPERATING RULES (parts 91 to 106) > PART 91—GENERAL OPERATING AND FLIGHT RULES > SUBPART B—Flight Rules (§91.101 to §91.195-91.199) > 91.173—ATC clearance and flight plan required.