I found these two links which help you put together real life flight plans. You can get arrival procedures (STARs) and departures (DPs or SIDs) from myairplane.com. You can also get high-level and low-level charts. The charts are broken into sections - 'h' for high level and 'L' for low level flights. Los Angeles would be in h4. Chicago would be in h5.
Simroutes.com will give you the real life routes used by the participating ARTCCSs (Air Route Traffic Control Centers). These are much more logical than the routes generated by my current FS-2002 which seem goofy at times. I think they are generated by the sim program itself, and do not come from a stored database of real flights. Maybe this has changed with newer releases. Anyway, it's more fun and educational to put together your own flights and know that this is what the real pilots are using.
Thanks, nice links. 👍