Many years ago,ex SIN, I was PF and ATC liasion on our 747 while my gallant Captain and Engineer worked out how to get us down without the inboard flaps falling off, making the A/C unflyable.
The radar controller obviously had his form to fill in and all went well till he asked our edurance.
"At this time 6 hours 30 minutes but as we are dumping, in 30 minutes it will be 1 hour!"
It all went a bit quiet after that.