Now this blog entry could be about the interest rate on your bank account, buying things at Cord Camera, or even a scary movie. The point of no return conjures up thoughts of entering an old, spooky house, with cob webs, knight’s armor, and paintings on the walls where the eyes follow you as you slink down the long hallway, and pipe organ music playing demonic chords. That could all be true, but I want to talk about what the point of no return has to do with crossing large bodies of water, like the Pacific, while flying (enter more creepy pipe organ music).

Even though the term point of no return sounds ominous, and nervous flyers might think it would be one more reason not to fly, it really has everything to do with safety. On a typical flight from Hong Kong to L.A. as we fly across the Pacific, we depart the Japanese coast and head out for the West coast of the U.S. Because there is only water beneath us, or because there are limited airports available to us along the Alaskan Aleutian Islands, we come to a place in the sky where we no longer can return to the airports in Japan based on the amount of fuel we have remaining.

On our flight plan, we have lat/long coordinates that tell us when we’ve passed the point of no return, based on two airports, say Narita in Tokyo, and Vancouver. This point is often not equidistant between the two cities because of how the winds will affect a turn-around. However, we have this point of no return, or PNR, calculated for us so that in an emergency, we don’t turn back toward an airport we can’t get to based on fuel remaining. Prior to reaching the PNR, we tell ourselves that if we lose an engine, we will return to Tokyo, and once we’ve passed the PNR, we will continue to Vancouver. We always have enough fuel to get to one of these en-route alternate airports, or ERA’s. We can’t depart on our trip unless we have the fuel at any point along our route to get to a safe landing airport, and the PNR helps us to make a better decision on where to divert in an emergency.

The PNR is also helpful because the two airport choices may not be as friendly as Tokyo and Vancouver. They may be Cold Bay (shown on the left) and Shemya, both in the Aleutian Islands. Neither are wonderful places to visit, especially in the winter time, but I’d rather divert to Cold Bay because Shemya is a postage stamp in the middle of the North Pacific. The PNR is important because even though we may want to go to Cold Bay, if we’ve passed the PNR, it’s hello balmy Shemya for us.