Is there a way to "transplant" the '.air' file of one aircraft and apply it to anotehr?  I have a plane I like the dynamics on, but another plane I have has a great model but bad dynamics.  Is there a fix?
???

You can indeed transplant major sections from one file to another, as ozzy said. Just remember to back up the original files to somewhere safe first. Most of what's in the .air file is modified by what the .cfg file says, but there are points like braking strength where the .air file entry does control what happens.

Use Notepad to change the .cfg file (the M$ aircraft editor in FS2k2 Pro is pants) and AirEd (in the downloads pages) to edit the .air file.

The sections you have to leave as they originally were, are things like the contact points (or your model may be above the ground, or sunk into it), lights and smokesystem entries, as they are located to suit the model. The dynamics pieces that don't affect the visuals can be changed more or less at will, although you have to be a little careful with things like the fuel tank locations, as they can affect the plane's trim.

Good luck!