A government report says a federal program aimed at identifying the most critical aircraft maintenance risks routinely misses deadlines.

The report says the Federal Aviation Administration inspection program's weaknesses are undermining its effectiveness and could lessen the agency's ability to oversee the National Airspace System if not addressed.

The report is based on a three-year investigation by the Department of Transportation's inspector general.

It says inspections are sometimes delayed years or misdirected to less significant maintenance areas while more risky areas go uninspected.