The answer is simple. Just look at their website and compare it with REX.
O'Connor Airlines offers one flat fare rate.
Look at REX. They offer different fare classes and fares such as:
Fully Flexible
REX flex
REX biz
REX saver
REX net
REX child
REX senior
It takes more than just aircraft and pilots to make an airline.
Those back room accountants have a thing called Yield Management and it will claw your salary packages from the skies if you ignore it.