3. Criteria: a. Awarded to all members of the Armed Forces of the United States serving in Vietnam and contiguous waters or airspace thereover, after 3 July 1965 through 28 March 1973. Members of the Armed Forces of the United States in Thailand, Laos, or Cambodia, or the airspace thereover, during the same period and serving in direct support of operations in Vietnam are also eligible for this award. To be eligible for award of the medal, individual must- -

        (1) Be attached to or regularly serve for one or more days with an organization participating in or directly supporting military operations; or

        (2) Be attached to or regularly serve for one or more days aboard a naval vessel directly supporting military operations; or

        (3) Actually participate as a crewmember in one or more aerial flights into airspace above Vietnam and contiguous waters directly supporting military operations; or

        (4) Serve on temporary duty for 30 consecutive days or 60 nonconsecutive days in Vietnam or contiguous areas, except that the time limit may be waived for personnel participating in actual combat operations.