A regional airline and the Obama administration urged the U.S. Supreme Court on Monday to grant broad immunity from lawsuits to airlines and their employees who report potential threats or suspicious activity to the Transportation Security Administration.

The justices examined the scope of immunity under a post- Sept. 11 law—the Aviation and Transportation Security Act— during arguments in Air Wisconsin Airlines Corp. v. Hoeper. The airline is appealing a $1.4 million defamation award to former pilot William Hoeper.