Well, I've been reading the documents released by the NSA under the US FOIA. There are 42 documents in all. I thought I'd summarise what is there and comment where I find something worthwhile.
1. "In camera" affidavit of Eugene F Yeates-Citizens against Unidentified Flying Objects Secrecy v NSA (Civil action no 80-1562)
This is the famous 1980, 21 page secret affidavit by Eugene F Yeates, the chief, office of Policy at the NSA. It was provided to the District Court, District of Columbia when a private UFO group asked the NSA to produce their UFO documents. It is a sequel to a public affidavit, a copy of which follows later.
In summary, it states that 239 relevant documents were located in NSA files. 79 originated with other agencies. 1 document included, was outside of the FOIA request. 1 document was declassified and released. Two other non COMINT records were released. The remaining 156 documents are with held and are COMINT reports for the period 1958-1979. 154 of these were based wholly upon intercepted communications of foreign governments transmitted on non-public "government net" communication links or systems.
The affidavit argues that "Revealing the contents of these reports would disclose the capabilities of NSA to target these government controlled communications systems." "...foreign intelligence services would be able to evade or defeat portions of NSA's present foreign intelligence efforts targeting international common carrier links." "Because each record and each portion thereof is properly classified under Executive order 12065, it is exempt from disclosure pursuant to 5 U S C S552 (b) (1)."
In summary the NSA argued that the COMINT reports should not be released to the general public.
Comment: From an intelligence perspective the NSA is correctly stating its position. Full release of the documentation would most likely cause problems.