No, it's not World War 2 again... it's a massive flyover of vintage WW2 bombers and fighter.
If you're downtown near the National Mall or along the flightpath, go out around noon to see the "Arsenal of Democracy Flyover" dominate the DC skyline. (They should be over the Lincoln Memorial by 12:10pm, headed over the Mall and then left after the Capitol.)
And here's a cool Plane-Spotting Guide to help you identify the planes (over 70 are scheduled to participate). Considering these are all prop-planes, it should be LOUD and glorious.
Update -- now with far away pix!