The US Federal Aviation Administration (FAA) has intensified an investigation into whether airlines complied with mandated flight reductions imposed during the US government shutdown. In early November, the agency ordered carriers operating at 40 major airports to cut daily flights, as it sought to ease pressure on air traffic controllers who were working without pay and facing rising absences.

There were reports that some airlines did not comply with the capacity reductions. Now the FAA has sent letters to airlines operating over ten daily flights at these airports, giving them 30 days to provide evidence of compliance. Companies that exceeded the limits could face fines of up to USD75,000 per flight.