I expect there are quite a few people who could help you with this...I can make heat blur in a rough and ready way, though many people are far better than me...

1. I copy the original layer.
2. On the background layer I use the lasso or pen tool to select the area for jet wash behind the engines, making sure I don't cover parts of the plane that shouldn't be covered.
3. I apply gaussian blur to that seleced area
4. I apply ocean ripple or some other ripple effect
5. I sometimes apply motion blur or smudging near the engines to try to make it look like the jet is blasting out
6. I deselect the area so it's part of the pic
7. I rub out the edges of the jet blast partially with the eraser on low opacity so the edges are not so clear cut - though I've seen pics with jet wash that looks clear cut...
8. I merge the background layer with the foreground - but before that I play with the coverage (?) of the background layer so the effect is even less pronounced.

It's done.  It really needs pictures to explain it properly, and my PS is in Czech so I don't know what things are called in English, and I'm at work so I can't see the program interface, but still, might be helpful to start you off. Screenshotart.com used to have great tutorials on stuff like this but I can't find them now - might be back later, they seem to be reorganising their site.

Cheers

Krigl