The head of the Federal Aviation Administration has not sold off his multimillion-dollar stake in the airline he led since 1999 despite a promise to do so as part of his ethics agreement, according to a Democratic senator.

In a letter to Bryan Bedford this week, Senator Maria Cantwell stated he vowed to sell all his shares in Republic Airways within 90 days of his confirmation, but 150 days have now passed. Bedford’s financial disclosures estimated his Republic stock to be worth somewhere between $6 million and $30 million. Republic completed a merger last month with another major regional airline, Mesa Air Group. Republic’s stock closed Thursday at $19.02, nearly double what it was before the deal announced in April.

It appears you continue to retain significant equity in this conflicting asset months past the deadline set to fully divest from Republic, which constitutes a clear violation of your ethics agreement. This is unacceptable and demands a full accounting, Cantwell said in the letter.

Bedford declined a request for comment, and an FAA spokesperson said he plans to respond directly to Cantwell.

The agency has been in the spotlight since January, when an airliner collided with an Army helicopter over Washington, D.C., killing 67 people. The investigation has already highlighted shortcomings at the FAA, which failed to recognize an alarming number of close calls around Reagan National Airport in the years beforehand.

In the spring, technical problems at the center directing flights into New Jersey’s Newark Liberty highlighted the fragile and outdated system relied on by air traffic controllers. In the fall, a longstanding shortage of controllers led to thousands of flight cancellations and delays during the longest government shutdown as more controllers missed work without a paycheck. Bedford has pledged to prioritize safety and upgrade the nation’s outdated air traffic control system.