These routes were probably generated internally at UAL, and are thus the product of their own flight planning system. Don't know what data format they're in, or if whatever program they're used for is available to the general public.
Most routes are very easy to figure out, in that one either:
1/ Files the pref route in the AFD (airport facilities directory), or
2/ File the shortest route based on distance or winds aloft.
Both scenarios assume that one is using SIDs(DPs) at the takeoff point, and STARs at the landing airport.
If you have some specific city-pairs, I'll see what I can find for you...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.