United said its operations are being held up due to the absence of furloughed inspectors from the Defense Contract Management Agency "who audit and approve operations throughout the manufacturing process for military products."
Spokespeople for the Defense Contract Management Agency could not be reached for comment -- they're furloughed, too.
Shutdown: What is closed
United had more than $4.6 billion in federal contracts for the 2013 fiscal year, sixth-most among private contractors, according to the Office of Management and Budget. In all, the government was slated to spend $357 billion on contractors for the year.
Contractors have also taken hits in past shutdowns. While federal employees have been compensated for lost wages following previous shutdowns, contractors as a group haven't been reimbursed.
A shutdown would "harm our economy unnecessarily when it is only slowly recovering, resulting in widespread ripple effects and a loss of public confidence," Cord Sterling of the Aerospace Industries Association said last week. The association includes major contractors like Lockheed Martin(LMT), Raytheon(RTN), Northrop Grumman(NOC) and Honeywell(HON).
The National Association of Government Contractors released a survey on Wednesday of 925 of its members showing that 29% planned to delay hires are a result of the shutdown.