> Airbus sued the Air Force after losing the KC-X contract
You have it backward. Airbus won the contract initially. Boeing sued and managed to get the bidding process restarted from scratch. Boeing won that second bid and Airbus decided to not protest, probably because they knew they had 0 chance against Boeing lobbying power in the US.
Trying to a void a lawsuit is how you get nonsense like the LCS where the Navy first opened the bids for a single class of ship, and then when it was time to announce the winner, split the contract between Marinette Marine and Austal.