Please note that this app is only for small planes. Large commercial aircraft, when the engines quit, have the aerodynamics of a brick which will preclude safely landing; however, your iPad can quickly locate an “Oh Sh!t Prayer” in the religion or non-religion of your choice.
I disagree with your assessment that large commercial aircraft have the aerodynamics of a brick. Two examples: the miracle on the Hudson and the Gimli glider.
That is not true at all. Commercial airliners GLIDE at a ratio of about 15:1, which means for every foot they descend, the travel horizontally fifteen feet. A nice glider for two people can do about 40:1. You can think of of all aircraft as gliders, some of them powered, if that makes it easier for you. As for size, most ultralight aircraft have a glide ratio of less then 10:1, but they are going so slow they are more like a parachute than a glider, not that they won't kill you anyway if you land into a brick wall.
What this means is that a commercial airliner, flying at 40,000 feet above the ground, could cut the engines and glide for over a hundred miles without straining, and then land safely. Please don't post such trash to the contrary, there are some who would believe it, repeat it, and that is not helpful to anyone.