The FAA plans to call in—on an as-needed basis—some Aviation Safety Organization (AVS) employees, including safety inspectors, if the government shutdown is not resolved quickly, the agency says.

“If the furlough extends longer than a few days, we will begin to recall as many as 2,500 employees back to work incrementally, including safety inspectors, engineers and technical support staff, depending on need,” the FAA says in a statement.

The FAA’s furloughing of its 3,000-strong flight standards inspector workforce caught many by surprise, and is a break with precedent. In the last shutdown 18 years ago, only a few inspectors with very little service time were furloughed, says a spokeswoman from Professional Aviation Safety Specialists (PASS), which represents the inspectors. In April 2011, inspectors were exempted during preparation for a shutdown that Congress averted with a last-minute deal.

PASS says it has no details on how inspectors would be brought back. The recall “would be ‘as needed,’ whatever that means,” the PASS spokeswoman says.

Inspectors and their union representatives learned of the furloughs on Sept. 30, the day before the shutdown began. Their surprise was not based simply on precedent, but also because the U.S. Transportation Department’s (DOT) own shutdown plans, issued Sept. 27, lists flight standards field inspections as among the FAA functions that would continue during a government shutdown.

However, the plan also notes that only 310 of the 7,000-strong AVS staff would remain on the job in the first few days, while 2,490 more “would be initially furloughed but would be recalled incrementally over a two-week period.” While the DOT plan did not provide details, it is clear now that the 310 staffers are mostly AVS managers, mainly located in field offices, while the 2,490 figure includes safety inspectors.

Further adding to the confusion, the DOT’s plan lists as exempt from furloughs another FAA 3,000 staffers “supporting lawful continuation of other functions,” including safety, though it does not specify what FAA organization they work in.

It is also not clear whether AVS managers are conducting any field inspections, though several sources with knowledge of the situation say there is no evidence checks are taking place.

The FAA’s airport inspector workforce remains on the job because it is funded through the Airport Improvement Program, a multi-year appropriation not touched by the budget stalemate that caused the shutdown.