WASHINGTON (AP) — The Supreme Court questioned Monday whether a Wisconsin airline can be held liable for reporting one of its pilots as mentally unstable and potentially armed. Federal authorities pulled the pilot off a flight on which he was a passenger, but found no cause for concern.

The justices heard Air Wisconsin’s appeal of a $1.4 million defamation judgment in the case of veteran pilot William Hoeper. The dispute centers on the immunity Congress promised airlines in a post-9/11 law aimed at encouraging them to report possible security threats.