Alpine Air reported that a cargo hatch on the twin-engine turboprop opened during the flight between Billings and Kalispell and the pilot was unable to close it. The plane carried about 3,000 pounds of mail.
Postal workers aren't sure any mail is missing, but if any is, they say it's likely two bags, or about 25 packages.
Weather hampered the search on Thursday for the bright orange mail bags.
Kalispell customers who believe they're missing priority mail packages are asked to call the Kalispell Post Office.
Information from: KCFW-TV, http://www.kcfw.com