Northwest Airlines has presented its pilot union leaders with a plan to start a new subsidiary specifically to replace the airline’s aged Douglas DC-9s with 70- to 100-seat regional jets. Employee compensation would fall to levels common among regional airlines flying 50- and 70-seat RJs, meaning Northwest’s DC-9 pilots would earn about half what they earn now and lose pension and 401(k) benefits. ALPA called the proposal “disappointing.” Tentatively called Newco, the new division would not supplant regional partners Mesaba or Pinnacle Airlines, but it would end their chances of flying jets carrying more than 50 seats as Northwest Airlink.