CLEVELAND, Ohio — United Airlines told ramp workers and counter agents at 28 airports Monday that it may turn to vendors to perform their jobs.

United said it may outsource up to 2,000 positions at the airports to companies that would do the work more inexpensively. The jobs include “under-the-wing” positions such as ramp workers and baggage handlers, and “above-the-wing” jobs, including customer service and ticket agents, all represented by the International Association of Machinists and Aerospace Workers union.

Cleveland Hopkins International Airport is not among those where United said it’s considering outside vendors.

The affected airports are in Anchorage, Atlanta, Billings, Boise, Fort Myers, Greensboro, Hartford, Indianapolis, Jacksonville, Kansas City, McAllen (Texas), Miami, Nashville, Oklahoma City, Omaha, Ontario (Los Angeles), Norfolk, Providence, Raleigh-Durham, Richmond, Reno, San Antonio, San Jose, Sacramento, Spokane, St. Louis, Tulsa and West Palm Beach.

Last fall, United outsourced about 635 jobs at 12 U.S. airports. In 2013, it turned to vendors at six U.S. airports and three in Canada, involving about 500 jobs.

But 236 employees at three airports in Hawaii in July voted to accept concessions to keep their jobs.

United will meet with IAM representatives “to explore possibilities for keeping this work in-house,” spokesman Luke Tunzenberger said of the latest belt-tightening.

“This boils down to making sure our costs are competitive.”

IAM leaders could not be reached Monday afternoon.