Although you asked about metering, I find the shutterspeed is more important for older prop planes. To achieve a blur for prop planes, you should be in the 1/200sec to 1/320sec range on the shutter. Ideally, you'll be in manual to control both the shutter and aperture so you have wing-tip to wing-tip depth of field. The acrobatic planes can be in the 1/400sec range.

I don't trust any of the partial meter readings and whether they will actual meter what is relevant for a moving subject. Did I really have a 5% portion of the frame exactly on the relevant portion of a fast moving subject? Rather, Sony's "Multi" will meter the entire frame and you can predict how it will respond to a blue (or cloudy) sky. If you use Shutter or Aperture priority modes, use a +1 EC to tell the camera to brighten the frame so you don't end up with a noisey underexposed sky. In manual, adjust the ISO to position the meter at +1 over the 0-mark.

For the actual day, take some test shots even before the planes are in the air. If you have some white clouds where the planes will fly, use them to confirm if you can push the exposure more to the right. If the clouds are blinking in the test images, you have the ISO too high. Use f/8 to f/11 for the depth of field and to give some options of the ISO at or above ISO-100. If the clouds in your test image are not blinking with the meter at +1, test where they start blinking as you push the exposure to the right. You may be at +1.3 to +1.7 to the right of the 0-mark, depending on the sky and time of day.

The image below is 1/250 sec (for the blur), f/10 and ISO-125 at an extended 600mm. The image was brighter coming out of the camera than the edited result. The whites were white without being over exposed. On a similar day to the example below, if you fixed your shutter at 1/250 in shutter priority and the ISO at ISO-100 with the EC at / around +1, the camera will handle the aperture easily between f/8 and f/11. You just have to pan, focus and shoot.

Final tip, capture the planes at their closest point while still coming toward the camera and passing. After they've passed will an easier shot, but less interesting. It can take all day (or multiple days) to get your panning technique so that you smoothly track the moving subjects and release the shutter in 3- to 5-frame bursts. Each plane will likely make several passes, practice and prepare with each pass, and hopefully at least 1 excellent keeper comes from every plane.

Warbirds over Oshkosh by Paul Sager, on Flickr