Diagonal Ceiling Crack throughout Living Room - Serious?

[Alex May]

Hello! 

I am considering a condo unit in the downtown Chicago area. It's a 20-year-old building located right next to the train rack. The unit's ceiling crack has grown throughout the entire living room diagonally. I've noticed that some other units have ceiling cracks too but not this long. Does anyone have any experience in similar issues and know if it indicates any serious structural damage or it's just a settlement / painting issue that can be fixed permanently?

Thank you!