In this particular example pre-flight briefing information proved to be 100% wrong - which is why I consider any pre-flight DA status info as a possibility only, best to verify by talking to the appropriate unit.
I used to fly relatively uninhibitedly VFR in Maryland. A regular sightseeing trip with visitors was a circumnavigation of DC at <1200' amsl, which allowed close, low, slant views of Mount Vernon, Capitol Hill, Andrews AFB, Fort McHenry, .. without talking to anyone.
Since 9/11, I gather from friends still flying around there, the permanently restricted areas are much larger and more aggressively policed (armed jets and helicopters, threat of huge fines and federal prison ..), so VFR bimbling is much more difficult. But there is also a temporary corridor, activated by NOTAM, between DC/Andrews and Camp David. Trouble is, there is no notice of such activation, presumably to avooid giving advance notice of Presidential or other VVIP travel; nor is it put on any broadcast. But ignorance is no defence, so VFR bimblers have to treat as active at all times, although it very rarely is.
Just to make the point that GA flying in US can have issues like ours.
[but I agree, it would be helpful if long, predictable, planned, inactivity of DAs were known to local ATSUs and on local ATISs, as well as being NOTAMd. The French system of having a predictably authoritative, daily updated, website of activity would be great. In UK, of course, 'someone would have to agree to fund it'. ]
(mere guide at) Jet Age Museum, Gloucestershire Airporthttp://www.jetagemuseum.org/
TripAdvisor Excellence Award 2015http://www.tripadvisor.co.uk/Attraction ... gland.html