Welcome to the Photosynth community, efbld2f!
First and foremost, if you haven't already downloaded the Photosynth Photography Guide, you can get it here: http://photosynth.net/help.aspx#photosynthhelp
There are a lot of important tips in there like not moving more than 25 degrees around something between two individual shots of it and getting three shots from three different positions of any part of the object or scene that you want to see in the point cloud.
I know you may be thinking, "I took more than three photos of the plane!", but try to think of individual parts of the plane. Take the rear wings, for example. How many photos can you see them in and did you move more than 25 degrees between those views? Where you did, the matching will likely fail.