The 12-to-6 vote by the union leaders highlighted the deep divisions over who will fly commuter jets.
The Canadian-made commuter jet was filled to near capacity, with 47 passengers and 6 crew members, the airline said.
The company's aircraft division, which is developing a new 50-seat commuter jet and a military fighter, is also losing money, analysts said.
The Yakovlev Yak-77 was a planned large business or regional commuter jet.
They were also concerned that Northwest would shift their workload to smaller commuter jets flown by pilots who are paid less.
The company received orders for 38 commuter jets in the year to Jan. 31, down from 209 the previous year.
Other analysts, however, have held out hope that the restructuring of major airlines will increase demand for small, relatively flexible commuter jets.
She has survived a crash landing on a small commuter jet.
Four Chevron executives were among the 44 people killed in the crash of a commuter jet on Monday.
Maybe, but the 20-knot winds, 4-foot seas and rain that prevailed rarely sink boats the size of a commuter jet.