Need advice for finding Summer REUs for AE

<p>I'm a mechanical engineering student, currently a sophomore. I want to switch to aerospace engineering when I apply to graduate school tho, so I think I should acquire undergrad research experience in AE. When do students usually apply to REUs? I looked on the NSF site and I couldn't find anything about aerospace engineering. I tried searching schools, but not a lot of info was given. Can someone give me some advice about when to apply and just general info. Thanks.</p>