When an ATS flight plan has been submitted for a controlled flight, the flight plan should be amended or cancelled in the event of the off- block time being delayed by :

During an IFR flight TAS and time appear to deviate from the data in the flight plan. The minimum deviations, that should be reported to ATC in order to conform to PANS- RAC, are:

An aeroplane is on an IFR flight. The flight is to be changed from IFR to VFR. Is it possible? flight".