Elon Musk is testing the limits of legal and ethical restrictions on the role of special advisers in U.S. presidential administrations, according to some legal experts and lawmakers who oppose the billionaire's mission against what he deems wasteful government spending.

His announcement comes after an outage last week to the primary system that provides pilots safety alerts in real time.

In a letter on Thursday, the lawmakers urged deputy inspectors general at several federal agencies to investigate potential national security breaches involving Musk's team. Those agencies include the U.