Consumer advocate Ralph Nader, whose grandniece was killed in the March crash of a 737 Max jet in Ethiopia, is accusing the Federal Aviation Administration of being beholden to Boeing.

The FAA is hosting dozens of international aviation regulators in Texas on Thursday to discuss the ongoing review of the Boeing 737 Max jets, which the agency and others around the world grounded in March after two deadly crashes that happened less than five months apart.

In an interview with CNBC's Phil LeBeau, Acting FAA Administrator Dan Elwell reiterated that the agency has no set timetable for allowing the Max planes to return to service.

Elwell also responded to Nader's criticism, saying he has "great respect" for Nader's work on consumer product safety. But the FAA chief said on "Squawk on the Street" that his agency is the expert on whether or not to green light the Max for service again.

Nader, in an earlier "Squawk Box" interview Thursday, called on federal regulators to recall the jets, saying the issue is not about how much the software may "overpower the pilot" or "empower the pilot." He said: "The basic problem is the design of the plane. And there is no way you can fix that without recalling the plane, the way they recall cars."

Some U.S. aviation officials believe a bird strike may have contributed to the crash in Ethiopia, feeding faulty data into one of the plane's autopilot systems. Crash investigators have indicated that bad sensor data triggered an anti-stall system aboard the Ethiopian Airlines flight that went down shortly after takeoff, a similar scenario to the crash of a Lion Air jet in Indonesia.

"In all the product defects that I have worked on over the years, I have never seen so many whistleblowers [and] so many authentic aerospace experts condemning the Boeing practice here," Nader added. "The FAA has been in the pockets of the Boeing company for years — pressured by Congress and the White House on both parties to cut budgets, to cut staff, [and] reduce their talent pool to oversee Boeing."

Nader said he sent letters to the FAA and Boeing and never got a response. "Boeing had a good record for 10 years or so. But that does not allow Boeing to have any free crashes that are preventable by standard aeronautical safety stability."

Nader's grandniece, Samya Stumo from Massachusetts, was among the 157 people killed in the Ethiopian Airlines crash shortly after takeoff from Addis Ababa. The other crash involving a 737 Max was in October, when a Lion Air flight went down in Indonesia's Java Sea, killing 189 people.

Boeing was not immediately available to respond to CNBC's request for comment.

— CNBC's Leslie Josephs and The Associated Press contributed to this report.