When we try to add this template:
http://en.wikipedia.org/wiki/User:Jay8g/sandbox/Template:Airline fleet table/Start
the TemplateData does not appear in the dialog.
If we add the doc subpage directly:
http://en.wikipedia.org/wiki/User:Jay8g/sandbox/Template:Airline fleet table/Start/doc
then TemplateData appears.
We have already made at least three null edits to the template. I assume that the problem is due to the namespace, but it's not bug 52609, because the template itself adds correctly to the page:
{{User:Jay8g/sandbox/Template:Airline fleet table/Start}}
Version: unspecified
Severity: normal