within a few months, the 717's abilities became clear to qantas, being faster than the bae 146, and achieving a higher dispatch reliability, over 99%, than competing aircraft. maintenance costs are low: according to airtran airways, a c check inspection, for example, takes three days and is required once every 4,500 flying hours. (for comparison, its predecessor, the dc-9 needed 21 days for a c check.) the new rolls-royce br715 engine design is relatively easy to maintain. many 717 operators, such as qantas, became converts to the plane; qantas bought more 717s to replace its bae 146 fleet, and other orders came from hawaiian airlines and midwest airlines.