Delta Air Lines has boosted maintenance spending on some of its older narrowbodies to help bridge the gap to anticipated deliveries of the airline's Bombardier C Series aircraft, the airline says. "With the mitigation of the C Series delay that we've seen, we've got a bit more work to do on the existing fleet versus expecting that the new aircraft [are] going to deliver for the summer schedule," CFO Paul Jacobsen told analysts on a January 11 earnings call. Delta has 75 CS100s on order, but ...