Delta Air Lines Inc. is looking to drop money-losing flights in 24 small cities, putting some localities at risk of losing air service altogether.

The carrier's list of endangered routes includes two daily flights between Salt Lake City and Butte, Mont., served by Delta partner SkyWest Airlines. Aircraft type for the route, which flies on average 65 percent full, is the 50-passenger CRJ 200.

For that route, Delta does not get what is known as an Essential Air Service (EAS) subsidy, according to spokeswoman Kristin Baur.

Federal subsidies help pay for flying into and out of 16 of the 24 cities. The carrier says it will ask for subsidies in the other eight cities because it can't afford to keep flying to them without assistance. Other airlines can bid for existing subsidies if Delta wants to pull out.

Last week's filing with the U.S. Department of Transportation kicks off a 90-day period in which the DOT can seek bids by other airlines to serve the routes. If an airline already gets a subsidy, it cannot abandon a route unless another airline takes it over.

The Salt Lake City-Butte, Mont., route could be abandoned, said Baur, adding that a "decision won't be made until we see what the DOT does."

Delta says it has been losing $14 million a year on flights to the 24 cities, which are concentrated in the nation's midsection, including locales such as Thief River Falls, Minn., and Waterloo, Iowa. Some flights are only 12 percent full on average. Many are on Saab turboprop planes, which Delta is retiring.

The Associated Press contributed to this report.