Komentar resmi
Make sure you aren't connected to the aircraft when planning distant missions. If you are plugged in, it will use the aircraft's current position as the anticipated takeoff point. After making sure you are not connected to the aircraft, you can navigate to the are you are trying to map and double tap to indicate where you plan on taking off. This will draw the purple dot. After that, all the distance checks will be done from that point and you should be fine.
If you want to do a bunch of layouts in a row, turn the iOS device to airport mode after doing the first one and it should default back to the same place.