They just need to man up and decide which one they want, then sole source it.
Sole source is going to be very expensive this time because just the first two batches are fixed price. With Boeing as the only manufacturer I'll expect some price increase.
Therefore I support a split buy. A special split buy. I call it a
competitive split buy
Each year Air Force is going to buy 16 aircrafts. For each year both competitors have to make a offer. If the costs of both aircrafts differ less than 1 % each company can build 8 aircrafts. Between 1 % and 2 % the bidder with the lower costs gets the option to build one aircraft more and the other company can sell one aircraft less. Between 2 % and 3 % two aircrafts and so on…
This is just an example. You can set span to 0.2 % or 2.5 %. As long as one competitor can’t offer a complying aircraft the other competitor can build all aircrafts for that span of time (1.5 month per aircraft). Solutions offered by one competitor may be used for the other aircraft to avoid development costs (boom).
Taxpayers are going to have a competition for years and save money.