What does one do presented with a light one wasn't expecting to see? Commonsense tells us we've not 'planned' or 'expected' to fly into a crane or a building! My reaction, and I'd guess, the instant reaction of an unexpected light is WTF!? If you check the rules, an instant response of up, down left or right isn't clear to the pilot.
Lemain, Are you not familiar with the rules of the air? I ask because you seem to be trying to put this in context of shipping.
The relevant rule says that where two aircraft are approaching head on, each turns right to avoid the other. Most pilots would instinctively turn to avoid anything ahead, especially if already at low level.
The rules also state that pilots needing to avoid should not pass directly below, or above another aircraft.
In PB's case, he would have been given a maximum altitude to fly, probably 1,000 feet QNH.