Contrary to popular belief, the specification issued by the U.S. Department of Defense are still around and in use. The military maintains three specifications for printed board performance requirements. To ensure compliance and quality, the specification require a qualification program.
There are two qualifications programs. The QPL and the QML. The QPL is the legacy program that has been in use for a number of years and cover many legacy applications. The QML is a new concept where the qualification is centered around the manufacturer rather than the end-item.
More info on the QML
Information Books: QML-31032 (from DSCC)(link)