DC: as nobody with a radio failure is going to be anywhere near the National ( I hope !), it is probably the lights of a corporate aircraft ( I've noticed the Falcon's flash ) or Southwest Airlines. All their 737's have flashing landing lights; yes, the right turn into DCA is as close to the old Hong Kong Kai Tak IGS 13 approach as you'll find these days. Great fun on a gusty day...
I've just thought - do SWA fly into DCA?