I have worked on 100% of my flights.
Now, there has never been explicit guidance to do this (or not to do this, might I add), but for me it makes so much sense...especially on flights longer than 90 minutes. No interruptions. Just you and your workstream and the satisfaction of being further along in the task at hand when you land than when you boarded.
To answer your question bluntly, though, if you own a major and/or dynamic piece of the work on your case and deadlines are approaching, the expectation from both your superiors and your subordinates is that you're working every chance you get...including on flights. :-)
All the best! :-)