AA1945 is used on multiple routes, but the most common is between Omaha, NE (OMA-Eppley Field) and Dallas, TX (DFW-Dallas-Fort Worth Intl.). If on a direct flight, you'll disembark the plane in around 1 hour and 55 minutes. Multi-stop flights can also use this number, as can services on other routes.
There's every chance you'll be on the Boeing 737-800 if you've booked a fare from Dallas, TX (DFW-Dallas-Fort Worth Intl.) to Omaha, NE (OMA-Eppley Field), a popular route for flight number AA1945.