system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the US government contract businesses about classified projects?

Like if they want a particular company to help them on a project, but the project is classified (I.e. A not yet disclosed airplane or something to that effect), how do they approach the company and what do they tell them?
If that makes any sense, I'd love to know. Very curious about this.
gpt
The initial contract bidding proposals are themselves vague and unclassified, but detail the Company clearance level (FCL) and Personnel Clearance level (PCL) requirements.

Cleared companies have network links with the Gov for when these contracts are being put out as Requests for Proposals (RFPs).

The Cleared companies then submit their RFP, which includes budgets, manpower, etc, etc, etc...  This then results in the Gov comparing and contrasting the bids, usually going with the lowest bid by the best rated company (companies get project ratings almost like an EBAY seller as they complete projects for different Gov entities).

The winning company is issued a DD-254 form (Department of Defense Contract Security Classification Specification) along with all the "Normal" contract stuff.

The DD-254 grants the company the ability to work that specific cleared contract, to clear personnel to work the project, and (if listed) to subcontract parts of the job to other cleared companies by issuing sub-contract DD-254's.

If that subcontract company already has a FCL (as listed in the ISFD database)it is a relatively simple process to bring them in to work.

If they are a totally uncleared company, it depends on what the subcontracted duties are...  for example, a Cleared company has the contract to maintain all services for an embassy overseas somewhere... they handle electrical work, plumbing, HV/AC, etc inside, along with maintaining exterior beautification.  All the people working inside the building will have PCL's and be part of a cleared company, but the company can hire a local uncleared company to handle Lawn services outside the embassy, simply assigning one or two cleared people to overwatch them when at work.

Now, if, for example, The Gov starts a project to train combat small drone operators... they decide they need to hire a company with a team of skilled maintenance techs to maintain the drones, and there isn't any such company out there, but there is a local company who does that exact work for a local Drone racing circuit...  The Gov or a Cleared company would approach them with the idea of becoming a cleared company or forming a LLC sub-company that could then be sponsored for a FCL to work classified contracts and then get it's workers clearances to work the project.  It's a rather complex process, but it how almost every cleared company got its start sometime in the past.