You need 50K elite qualifying points (EQP) for Platinum. In premium economy classes and above, AA allots 1.5 EQP per flown mile, so 33.3K flown miles will earn 50K EQP.

With your flying patterns it might behoove you also to think about BA. It sounds like you could easily qualify for BA Silver (= AA Platinum = Oneworld Sapphire) which would get you mileage bonuses but also permit access to AA lounges even when traveling domestically on US or Canadian itineraries. You'd need 600 tier points (for example, one-way TPAC or TATL in J earns 120 tier points, 140 if on BA metal) for Silver, which certainly sounds doable. (You'd also need to fly 4 segments on BA metal during the year, which might or might not be an issue.) Look at the tier point tables that you can find on the BA board. Short-haul redemptions using BA Avios can be good value compared with AA redemptions (long haul not so much) but BA's upgrade options (MFUs) are way better than AA's.