# Talk:Lockheed D-21

There is no point to any related development links in the See also section if they're already linked in the lede of the article.--Sturmvogel 66 (talk) 18:03, 19 December 2016 (UTC)

Several sources I've read claim that there were actually five operational flights in the D-21 program, and that the exact details of the fifth are still secret. Naturally, due to the very nature of these rumors they may be impossible to confirm or deny, but I wanted to bring this up here before putting it in the article.  — Preceding unsigned comment added by 68.81.176.133 (talk) 00:06, 2 April 2018 (UTC) 

Be prepared to defend your sources. Self-published books, etc., will be deleted as not meeting WP:RS.--Sturmvogel 66 (talk) 00:41, 2 April 2018 (UTC)
This article, which was written by a former SR-71 crew chief, mentions there being five operational D-21 missions but says nothing about the nature of the fifth one. I have encountered mention of a fifth, classified D-21 flight elsewhere as well, but mostly on message boards and forums that do not meet Wikipedia's standards. It's certainly possible, since some aspects of the SR-71/A-12 family's operational history are still secret. For example, the SR-71's top speed is officially Mach 3.3, but reports say it could reach Mach 3.5. An extra D-21 flight or two seems like the sort of thing that they might still be hiding. unsigned comment added by 24.224.66.196 (talk) 00:06, 25 May 2018 (UTC)
That article (http://sr71.com/srlink~1.htm) is only a web page with a long list of links on it.  This isn't even a decent reference and there's no direct way to check on this supposed 5th mission. -Fnlayson (talk) 21:52, 31 May 2018 (UTC)