AA employees except for officers (who are provided with memberships) and managing directors (who can pay) are prohibited from joining the club. Retirees may join. As can spouses of employees. Back when I first started with AA, an employee's spouse could join and then buy a spousal membership for the employee. This went away sometime in the late 90's, early 00's.

Employees in uniform generally should not be in the club. I can think of a few reasons why they would be, at least for a short visit. I know when I interviewed for a manager's job at a certain AAirport back when I worked for AA, I was invited to wait in the club for the interview. I didn't have so much as a sip of water. But I did sit in one of the chairs. Speaking about DCA specifically, the general manager's office is connected to the club, and while there is an alternate method of access to their office, it's not unusual for people visiting the general manager to transit through the club....or at least be seen in the vicinity of the club.