Finally, assuming your signal is successful, you’ll need to be able to understand the signal being sent back to you. If an airplane flies overhead and rocks back and forth, dipping its wings consecutively, your message has been seen and is understood. At night, acknowledgment of a signal is accomplished by repetitive flashing of a green running light. If they have seen your signal but do not understand, they will fly a circle above you. In this event, you need to make every effort to clarify your situation. Holding your arms up in a Y pattern will indicate that yes, you do need help. Holding one arm up and one arm down, signifying an N shape, will indicate that no, you do not need assistance.