Dear Ms. Clark,
Thank you for posting your request on History Hub!
Military records in the custody of the National Archives do not include flight manifests, cargo manifests, or passenger lists. These are not considered permanent records. Under normal Department of the Air Force records management procedures, such documentation would be destroyed after initial administrative use.
We suggest that you request a Certificate of Witness to Marriage Abroad from the Department of State for your relatives, Samuel and Lisa Clark.
Since marriages in Germany require the officiant to register the marriage at the local state registry office, please review the information on the FamilySearch wiki for Germany Civil Registration to determine the local state registry office (standesamt) you need to contact.
We hope this is helpful. Best of luck with your family research!