Most tele/zoom lenses lose their autofocus function when used in conjunction with a tele converter. However for high aircraft shots I guess you'd manually set infinity anyway. Just thought I'd mention it.
I upgraded from D70 to D300 about 3 years ago and find it an excellent all-rounder. Ideal for plane shoots.
Most of the stuff I do is sports photography (Rugby League) and although the D300 works well at high-speed/ISO in good light, it…"