Ahh, the fun of contrail shots.
There's a real element of luck in whether you can get good shots like these, mostly revolving around how well lit the plane is (or rather the direction of the light) and how messed up the air between you and the plane is. If you're shooting an aircraft that's backlit like your BA 747 then there's unlikely to be much chance of it really working. Unless you're specifically after silhouette shots or some other similar effect then backlit planes tend not to work too well at the best of times, never mind when it's miles away from you! By the time you've corrected the exposure it just looks... Well... Kinda wrong.
So the first part of getting good contrail shots is only shooting in light that's likely to work, i.e. when the light is hitting the same side of the plane you're seeing. In terms of settings, I generally stick to my regular aviation shooting mode (for jets at least) of Av and let the camera do it's thing while keeping an eye on my shutter speed to make sure it's quick enough for the focal length I'm using. With your 150-500, you say you were using it at 500mm? That lens probably won't perform as well at 500mm as it does at 400mm, so you might find you actually get a sharper, better quality image by zooming out a little but being able to crop into the image further in post-processing. That feels very counter-intuitive when you do it but it can work. You'll probably also actually get better results not using the 2x TC. People often assume that you need an enormous focal length to get good contrail shots but that's not true, even a 200mm lens on a crop body can get you close enough for it to work.
This was at 400mm on a full frame body, so quite a way out from 500mm on a crop body with a 2x TC. It's not a close-up of the aircraft but it's unreasonable to expect to get that with any standard telephoto camera lens, it still works well as a contrail shot though and there's still enough detail to tell what the plane is (although this is dropped down to 1200 from the original 1600 wide edit).
The real bit of luck is whether the atmosphere will actually allow a clear shot. Just the same as shooting aircraft across tarmac on a hot day will give you heat haze, if there are patches of air at different temperatures between you and the plane then the light will bend and distort before it gets to you. There's nothing you can do about this and no post-processing that can fix it, it's one of those things where you just have to wait for the right moment.
When you're asking about airports to visit for shooting, are you wanting to do more conventional aviation photography on these trips?
