Deutsches Museum Flugwerft Schleißheim is a 24-min train ride to the suburbs (40 minutes if your starting point is Deutsches Museum), and required a rather lengthy walk (perhaps about 20 minutes of brisk walk) across a laid back neighbourhood before you even reach the main entrance.
However, as an aviation enthusiast, I would say it was worth it.
Germany is strong, and it has a rightful reason for that: Engineering. Or rather, precision engineering. This is supported by a strong culture and belief in sciences, and this is most obvious in Deutsches Museum in Munich!
If you are easily bored out by repetitive stuff (i.e. Mozart here and Mozart there), or are short of time, spend time on Makartsteg bridge (just off Mirabel Palace) and soak in the beautiful sight of Salzburg along the riverside.