DR Jane, as an old L.A. airport watcher, I had a few favorite spots at LAX:
The one on Aviation Blvd. was right across the street from the eastern end of the south runways. You could stand there right underneath the jets on their last few seconds of landing approach. (Jeez, did I use hearing protection when doing that??) As I recall, there was just enough space for a few cars to turn into. I'm looking at the birds-eye views on Bing Maps, and can see that it's completely fenced off now. Things have changed around airports.
People also used to park on those abandoned streets between the airport and the ocean. More distant from the runways, but you'd see a lot of takeoffs and landings from both sets of runways. I remember one windy day, watching the large jets battling the crosswinds on landing. They have that area tightly fenced off, too, not only for security but because they've basically allowed all of those streets to crumble. (I forget the history of that -- it was obviously planned to be residential originally (which is rather incredible), but did they ever build anything or was it abandoned after only the streets were put in?)
Another spot I liked was on W. Imperial Hwy. along the southern border of the airport. You can park on a little parallel street called Imperial Ave. that is elevated and provides a nice view across to the terminal and theme building area.