[zppln]

Software level design documentation in aerospace make extensive use of UML (my shop even use PlantUML). Sequence diagrams in particular are quite useful.

People often find that level of documentation a bit redundant if you have access to the code, but if you're pressed for time and the diagrams actually describe the crucial parts it can be a huge timesaver when you have to fix something in a 10 year old component.

[toyg]

Yeah, UML overall is a bit overengineered, but sequence diagrams can be incredibly useful.