WASHINGTON (AP) — Ruling that airlines have broad immunity from lawsuits under a post-9/11 security law, the Supreme Court on Monday threw out a $1.4 million defamation judgment awarded to a pilot who was reported by his employer as mentally unstable and potentially armed.

The court was unanimous in holding that a law aimed at encouraging reports of possible security threats to the Transportation Security Administration shields airlines from defamation claims when the reports are substantially true.