Rules of the Air Article 72

Unless otherwise prescribed by the appropriate authority, an aircraft electing to change the conduct of its flight from compliance with the IFR to compliance with the visual flight rules shall, if a flight plan was submitted, notify the appropriate air traffic control unit specifically that the IFR flight is cancelled and communicate thereto the changes to be made to its current flight plan.When an aircraft operating under the IFR is flown in or encounters visual meteorological conditions it shall not cancel its IFR flight unless it is anticipated, and intended, that the flight will be continued for a reasonable period of time in uninterrupted visual meteorological conditions.