Last week, the service selected Boeing, Kratos, Northrop Grumman and General Atomics to receive indefinite delivery indefinite quantity contracts for the Skyborg program.

The next step involves the service meeting with the four companies to get a better sense of their proposed aircraft ahead of issuing the first order for prototypes anywhere over the next 60 to 90 days, said Brig. Gen. Dale White, who leads the Air Force's program office for fighters and advanced aircraft.

How many competitors move on to the next stage of the program is yet to be determined, and will depend on how many drones the Air Force can buy with its available funding. Although each of the four companies' contracts have a ceiling of $400 million, no money has been awarded yet.