Being unable (or should that be unwilling) to comply with the rules of the air is most definitely a hazard.
Yes one does wonder why (does the Navy issue Notices to Mariners saying "Navigation Exercise - participating vessels may not be able to avoid crashing into other shipping"?) However in practical terms one can do no more than one should be doing anyway, keeping a good lookout. In my yoof this was referred to in one Nautical Almanac as "the ordinary practice of seamen". I preferred not to ponder on what this might consist of.