I sent an email to Jack and it did not show as "undeliverable" but I have not received a reply. Have you tried "snail mail" to the address listed in the Alumni roster?
I never was stationed with Jack and have had no personal contact with him since my retirement in '81.
Glad he got in touch with you. Now I am wondering if he really did get my email - never heard back from him. Maybe he deleted it - kind of like ignoring a "FLASH" message !
Just got about 9" of snow here, more to come in a few days.