Urgency: Understanding PAN-PAN

A common urgency situation for VFR pilots is fuel emergency. If you calculate that your fuel state will not allow you to reach your planned destination, or even a nearby alternate, with a safe reserve, declare PAN-PAN immediately. Do not wait until you are at your destination and the tower refuses to let you land because a larger aircraft is ahead. Declare urgency, request the nearest suitable aerodrome, and get on the ground.

Example: You are HB-CDA, a Cessna 172, cruising at 2500 feet between Bern and Lausanne. You discover a leak in your fuel line. Your calculations show you have 40 minutes of fuel remaining. The nearest aerodrome is Payerne, 20 minutes away at your current speed. You declare: