As just about every US airport *except* DCA has now been recertified, I think the reason that DCA hasn't seems pretty clear. No, it's not because passengers would get a sobering look at the side of the Pentagon.
Quite simply, and this is only my own humble opinion, I don't think DCA will reopen anytime soon (if ever) due to its proximity to P-56 and all the other airspace over sensitive and public landmarks in the immediate DC area. If an aircraft were to be hijacked while DCA is landing to the north, any overfly of the DCA airport would happen so quickly that the aircraft would be hitting someplace before anyone could respond. It'd be one thing to see an aircraft on approach to runway 1 veer off, as a clue, but the situation would be all the more difficult to ascertain should a flight be approaching runway 19, already jinking down the river on the visual approach. Should they jink *left* at the last minute, and not *right*, it's the same story--they've impacted before a response can be effected.
One "solution" I've heard proposed on a radio call-in show was for the military to have helos orbiting in the area, armed and prepared to down any straying aircraft. Notwithstanding the military's ability to get off a couple of quick IR-guided missles (and assure they hit and down the aircraft in a timely fashion), I seriously doubt the government would want to be in the potential position of having to defend the downing of an innocent airliner that was just a couple of seconds too slow in turning. Oh yes, there's also the matter of collateral damage to those on the ground.
DCA has survived alot of things in the past, and the quick response of congresscritters opposed to having their convenient airport (complete with parking places) taken away has indeed be one of the main reasons why DCA has survived. I don't think the above congresscritters want to be viewed as putting personal convenience ahead of national security/public interest, and accordingly, I doubt DCA will ever reopen. If IAD or BWI is too far a drive for them, I'm sure some type of arrangement will be concocted whereby Andrews AFB will be utilized for them (better ground security anyways) and some rich corporate donor/sponsor provide use of their corporate jets to get in and out.
Hope I'm wrong, as DCA is a great airport, full of history, but history has now "changed" things, forever...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.