The Minecraft Launcher will display a white screen when launched without internet.

When I was on vacation in the country with no wifi or internet, I would sometimes launch the game and the launcher will display the average lines of code that come up when there is no internet. Then, the screen would turn to a solid white and the launcher would not load the update notes and profile editor and such. It would just remain a solid white window. To close Minecraft, you would have to FORCE-QUIT it. A normal quit doesn't work.