Comair is down to 290 flights a day. More than 1,000 Comair employees are in the Cincinnati/northern Kentucky area, 700 of them in Kentucky.
Comair has slashed its fleet, flights, and work force over seven years. Delta said the smaller planes' fuel inefficiency and maintenance make them too costly to fly.
"We just really couldn't get the cost structure to where we wanted to get it," said Don Bornhorst, senior vice president of Delta Connection and a former Comair president. "It ultimately was a cost issue; it wasn't a quality issue with Comair. They're a good airline, great employees, very innovative … We just could not solve the cost issues."
At Toledo Express Airport, Delta had offered flights through Delta Air Lines and Comair until 2008, when it halted passenger service. Delta had started service in Toledo in 1945.
Delta, based in Atlanta, had about 500 of Comair's 50-seat regional jets in 2008 and plans to reduce that to 125 in two years. Most of that flying will be done by new 76-seat jets as well as the 117-seat Boeing 717s Delta is leasing from Southwest Airlines.
Delta said it has stopped flying 16 of Comair's 50-seaters and will lease the carrier's other 28 planes to others.
Comair handles just 1 percent of Delta's flying, so its loss won't mean big changes to Delta's network. Besides Cincinnati, Comair has hubs in Detroit and New York.
Comair was founded in 1977. It started operating as Delta Connection in 1984 and became a wholly owned Delta subsidiary of Delta in 2000.
Aviation analyst Mike Boyd of the Boyd Group said he expected a Com- air shutdown because regional airline models don't work anymore.
"It's not going to turn around," Mr. Boyd said. "Delta is quite correctly saying, 'We've got to get rid of these uneconomic airlines.' "
Before entering bankruptcy protection in 2005, Comair had more than 7,000 employees and 1,160 flights. Comair and Delta emerged from reorganization in April, 2007.