What advice would you give to a high school junior looking to find an internship in their field of interest?

I'm currently an 11th grader in Texas, and it's been tough for me to find an internship relating to my field of interest (aerospace engineering). Although I have gotten recommendations from sources/connections, applying for them has been tough for me because most require me to be a U.S. Citizen (i.e. NASA). I'm currently in the PLTW Principles of Engineering class and plan on taking PLTW Aerospace Engineering and PLTW Engineering Design & Development next year. I want to apply the skills I've learned in my classes to real-life experiences but not sure what resources would help me achieve this.