There are a couple rules about internships. You have to be currently enrolled in an accredited university, generally a junior or senior (grad school work is acceptable, but not preferred), and 9 times out of 10, in an aviation related major. It's possible to get internships not satisfying the second and third requirements, but it's an absolute must to be a current university student, for liability reasons. Other than that, United is not give a whole lot of internships out right now, and the deadline is either fast approaching or already past (they've already scheduled interviews with the candidates at my school who were qualified and applied), and you may or may not be able to be able to choose LAX
excusively. Other than that, try giving a call to somebody in the HR
department, or even their flight operations department.
I'm not pro-Boeing or pro-Airbus, I'm pro-crew all the way.