Once upon a time (read: 2006), defense contractors didn't file legal challenges against their biggest customer on contract decisions even if they KNEW there was wrongdoing involved. (Lockheed Martin's loss of the original Small Diameter Bomb competition in 2003 comes to mind.)
But all that changed after GAO upheld the first CSAR-X protest last January. Raytheon is now protesting losing the Joint Cargo Aircraft award, and both CSAR-X protestors are re-protesting.
So, when Boeing pulled off a huge upset and scored the $2 billion contract to re-wing US Air Force A-10s, folks throughout the industry were watching to see if Lockheed would file a protest. Mind you, Lockheed was teamed with Northrop Grumman, which combined own the ongoing A-10 precision engagement program and Fairchild Republic's design right to the A-10. Boeing's victory would seem to be a huge surprise, and, in this day and age, thus ripe for protest.
Today, however, Lockheed has sent me a statement, saying the company "accepts the U.S. Air Force’s evaluation and execution of the A-10 wing replacement competition and award."