UA6019 serves multiple routes, but the most common is between Washington, DC (IAD-Washington Dulles Intl.) and Atlanta, GA (ATL-Hartsfield-Jackson Atlanta Intl.). If you're lucky enough to score a direct flight, you'll disembark the plane in around 1 hour and 56 minutes. Multi-stop flights can also operate under the same number, as can flights on other routes.
If you're on flight UA6019 from Washington, DC (IAD-Washington Dulles Intl.) to Atlanta, GA (ATL-Hartsfield-Jackson Atlanta Intl.), there's an excellent chance you'll be on board a Bombardier CRJ700. This flight number serves a number of routes, but this is the most common one.