I have run into several issues where flight schedules that would remain below 140 hours are not allowed. For example:
Say I have a 777-200 (2 General Electric GE90-77B) with 6 round trip flights to LAX-NRT each taking 21:53 for a total of 131:18. This should leave me with about 8.5 hours for another flight. But the plane is listed as having only 8 hours available, so when I try to fly LAX-MSP, which takes 8:06, the plane does not show up.