WATERTOWN, S.D. -

The federal Transportation Department says it will no longer subsidize Watertown airline flights through the Essential Air Service program.

Federal officials say the subsidy level in the city has surpassed $200 per passenger. Federal rules say any EAS community within 210 miles of a major hub airport must maintain a subsidy level below that mark, and the Transportation Department says Watertown is 207 miles from the Minneapolis airport.

Watertown Mayor Steve Thorson maintains the center of the city of 22,000 people is actually 4 miles farther west than under the government's measurement. That would put it outside the 210-mile limit. The city will seek a waiver.

If it isn't granted, subsidized flights to Pierre and Denver could stop by the end of the year.