The Boeing 757 and 767 are the only airplanes to share a common type rating. This is due, in part, to airplane systems that were designed so that one set of flight crew operating procedures can be used for both aircraft types. Airlines who fly both these planes will have more flexibility when it comes assigning crews because they’ll understand how each system works on either plane and adapt accordingly with changes in market demand among other things. Maintenance procedures will also go smoother since there’s not as much variation between two different models; spare parts inventories should reduce if airlines choose this option too!