The cost/hr column is calculated when a duration value is entered on new flights. Confirm you have values entered in the Options...Aircraft area then when making a new flight entry after the duration value is entered you see the cost/hr populated.
Sorry it took so long getting back.....been away. I confirmed all above. Interestingly, I have one of the planes with about half of it's entries showing the calculated costs and the other half not showing any cost.
This would be something you'll need to do via an export, change, import as it was decided not to offer this functionality at this time, here's why. Assume the cost/hr is a rental rate (the intended purpose). 6,000 hours ago it may have been $35/hour for a C-152. Today you enter a value of $XX/hour (whatever it is, obviously different, and more). It would not be accurate to apply a rate entered today to prior entries. HOWEVER, what we may do in a future release is offer this functionality and have it only apply to rows (flights) that do not have a Cost/Hr entered. Is this what you would like to see? I don't want already entered data to change, but you could apply a "apply to empty values" type of logic, in fact, probably something that could be done sooner if this would be acceptable. In fact, let me look at this, as I type I'm thinking of ways to make this work.