Hi Kris,
all of my airliners shots were taken with the cheapest Canon 300mm on the market. The
non-USM EF 90-300I've been very pleased with it, and it has been great for portrait shots too, provided sufficient distance can be put between yourself and the subject.
Obviously it works better in good light. In poor light the max aperture of f4.5 is limiting, as this allows less light into the camera, forcing either a higher ISO, or a slower shutter speed, or both.
The USM version of this lens offers faster and quieter focusing, I'm not sure how much this helps in reality.
The
75-300 IS includes the image stabilisation, which allows a slower shutter speed and therefore compensates for the fairly small max aperture of f4.5
Doug's
70-300 IS DO has a significant size advantage, using better optics to contain the same range in a much smaller, lighter barrel.
I have to admit that I have just gone out and got the Canon 100-400 L which Mark refers to, second hand off ebay. I have not yet had a chance to do any proper aviation photography with it, but unless you go for an L series prime lens (like Mr H) then it is *the* aviation lens. You do however pay for the privilege