The max distance between waypoints must be 2000 m or less. This includes the distance between the first and last waypoint. In other words, your last waypoint can be no more than 2000 m from the first waypoint to complete a one way mission. In order to do what you're trying to do, you must do the following:
- Plan your mission as a round trip (even though it's a one-way mission). Make sure your returning waypoints (even though you won't be using them) are no greater than 2000 m apart.
- When planning the mission, be darn sure to take into account any elevation changes or obstacles.
- Turn off SmartRTH (otherwise the mission will cancel and your bird will try to return home if it decides you won't have enough battery for the round trip- which you won't).
- Start the mission.
- Drive to your friend's house, being sure that you can get there before the bird does. This is the tricky part. Fly too slow and the bird will run out of battery. Fly too fast and it'll get there before you do. I have no idea if your battery will last for 26,000 ft but if you're confident that it will, go for it. Set your mission to "curved paths". If you set it to "straight lines", it'll briefly stop at each waypoint, adding extra time to the mission, time that is NOT reflected in the "estimated mission time" displayed by Litchi.
- Assuming you get there in time, cancel the mission once your bird is fairly close and then land manually. You might even want to add enough waypoints to circle your friend's house to give you a little extra time.
I had the same problems as you before I realized what I had to do. I did all of the above for an 11,000 ft (2.1 miles) mission and it worked perfectly.
The following video demonstrates a mission similar to your goal. Be sure to read the explanation below the video.