I probably have well over 300 flight plans in the software. Recently I saw a bunch of flights that I wanted to delete that were either duplicates or just had no routing in them. So of course I press the edit button, that I selected about five flights and instinctively I clicked on delete all. And then noticed it was taking an abnormal amount of time, and quickly realized that the software was working on basically obliterating all of my flights that I created over the years. It was a simple misinterpretation, but I feel that this button is far too risky.
Perhaps you could change the delete all to a select all, and then the delete button could say delete selected flights. This would make it clear to the end-user of what they are about to do and also make it a two-step process. Or maybe you can code the software that would allow a shift click where somebody would click the top flight on the list, scroll all the way down to the bottom, hold the shift key down and click the bottom flight, and then they could just hit delete selected that would remove everything that they intended to select. Please consider modifying this feature.