Illegal conjures up the fact there is something more dangerous in the flight
A private flight operated by a professional crew is as safe as one flown by the same crew illegally and remember the crew may be unaware although the statement illegal charter conjures up the image of cowboy pilots cowboy operation
The problem comes with insurance where the insurance would be deemed invalid if the flight was an illegal charter
Private jets flown by professional crew have a better safety record than AOC operations worldwide the fact that one is legal the other not doesn't make a jot of difference to safety but the insurance would be a problem if anything happened