nice set. I especially like the first and the third. I think mainly because each of them has just a little form to catch the eye. The first one has a little more of the mountain shape, and the third has the diagonal cloud.
It's hard to tell, but I guess I like 3 best of all, as the sky still shows quite a good amount of blue, and mostly because of the blown-apart, diagonal vapour trail which adds a really pleasing element to your composition.