"yetti" makes the point that one always has an IFR option in mind when planning a sortie. The point here is that the crew that flew the sortie DID NOT PLAN IT. Moreover the crucial waypoint of the Lighthouse was entered incorrectly into the TANS.
What we have is a crew who took over the task from another crew and totally ignored the rules on crew duty time, outbriefing and/or nightstopping out of theatre. They also ignored the rules on crew meals (when they took off on the fatal sortie NO crew member had eaten a proper meal for at least 10 hours). To this day nobody knows whether they intended to return to Aldergrove ignoring crew duty limitations or remain outside Theatre overnight without HQNI approval.
How many rules are you allowed to break before it is considered negligence?