Mark,
I have a sony camcorder (Hi-8) that works fine for my flight line films. The trouble, if I understand you correctly, is that you cannot see the airplane in the viewfinder. The trouble isn't the camcorder, but in the viewfinder. I dont know the specific's of your camera, but can assume one thing. It probably has a small screen to view with. The trouble is,when you view the video on a regular video screen, you have 525 or so lines of pictures to view. To show the same image on a 3" camcorder screen some of the lines have to disappear, as it can't fit all those lines on that little screen. I've seen a plane disappear on my screen, but when I play it back on the television, it is still there.
Only thing I try is to zoom in to find the plane, then zoom out a little and try to follow it. The further away and smaller the airplane the harder it is to video.
Personally I dont think buying another video camera will cure your problem, only empty out your wallet more.
I hope this helps your question.