No flight plan scheduled flight


When tracking flight my daughter was on ZT147/AWC147 Gatwick to Turin with a scheduled departure of 06.50 28th Jan (delayed), I could not get FlightAware to list any info.

When I clicked ‘Show hidden information’ it said flight plan not filed. Some 20 mins after landing, partial information was displayed.

How can a commercial scheduled flight not file a flight plan and fly ?? I could not get any other flight info app to even recognise the flight.