NK has agreed to sell its limited DCA slot portfolio (four slots, two pairs) to WN, which has the intention of starting double daily STL-DCA service pending DOT approval to "slide" the slots to commercially viable times. A brief summary of WN's application for exemption can be found here:
http://airlineinfo.com/Sites/DailyAirline/web-content/ost14/ost070312.html#southwest7312
Good news for STL, WN continues to grow in business markets.