How would an aircraft visually signal "in distress"? A ship at sea would fly its flag upside down to signal it's in distress. How does a plane or airliner that has no radio or transponder visually signal that it is in distress? 

This question: How do commercial pilots send distress signals? explains how it is done using a radio or transponder, but how could the message "please don't shoot me down" be relayed visually to a fighter pilot?
For the US, the FAA's Intercept Procedures list several things a pilot can indicate without radios:


Acknowledge instructions: rock wings, flash nav lights
Unable to land at indicated airport: flash landing lights
Cannot comply: switch all lights on and off at regular intervals
In distress: switch all lights on and off at irregular intervals