What is the test for extending the time period for a claim under Rule 4(m) of the Civil Aviation Act?

Rule 4(m) contains both a mandatory and a discretionary component. First, if a plaintiff shows good cause for the defective service, the district court must extend the time period for service. In re Sheehan, 253 F.3d 507, 512 (9th Cir. 2001). Second, with respect to the discretionary component of the rule, the district court has discretion to grant an extension even absent good cause. Mann v. Am. Airlines, 324 F.3d 1088, 1090 (9th Cir. 2003). The court's discretion in that regard has been broadly interpreted, and no specific guidelines apply. In re Sheehan, 253 F.3d at 1213.