Same as mine. On your profile you indicate AA and UA programs, both are strong in ORD, however I recommend you to decide on a primary carrier and try to get some elite level with them to maximize your benefits. You mentioned going to Frankfurt on March, and some travel to the West Coast for April and June. I strongly suggest you purchase your ticket, do not use miles, with AA for your March travel, enroll in the PLT challenge with AA, making your starting date on the 1st or 15th of March, depending on your travel dates, try to squeeze them so they fall within the 90 days. The 90 days challenge will take you through May, so if we add the miles to Frankfurt, plus the trips (no mention on how many or where to) to the West Coast that you should also book with AA you will be on your way to acquire PLT level with AA. Advantages of PLT or GLD level with AA are:
1) no check luggage fee ($15 for 1st, $25 for 2nd, $100 for 3rd)
2) better seat selection on flights, (Exit seats)
3) higher priority boarding, even though you are flying coach
4) higher security screening, even though you are flying coach
5) higher standby status
6) dedicated customer service
7) additional bonus miles for flight, 25% for GLD, 100% for PLT
8) accumulate 4 upgrade stickers per 10k miles flown to be used on domestic upgrades to 1st class while paying coach

Those are the benefits that I remember on top my head at this moment. Once you decide on which carrier to achieve your Frequent Flyer benefit I also suggest you enroll in their dining reward program and also get their credit card so you can accumulate more miles in the long run. Bottom line, try to maximize your flying experience. Currently, in order to mantain GLD with AA you need to fly at least 25k or 50k for PLT in a calendar year.