Rep. Stephen Lynch wants Republicans to hold hearings on the Transportation Security Administration’s “Quiet Skies” program.

The Massachusetts Democrat sent a letter to House Oversight and Government Reform Committee Chairman Trey Gowdy about the program, in which undercover air marshals reportedly monitor air travelers, MassLive reported.

Lynch said in his letter that while he “strongly support(s) the critical mission of the Transportation Security Administration to ‘protect the nation’s transportation systems,’ the administration of a covert surveillance program that targets nearly 200,000 air travelers, including U.S. citizens, per year without probable cause must be subject to robust congressional oversight.”

Lynch’s letter comes after a report by the Boston Globe that found that the TSA was regularly targeting travelers who “are not under investigation by any agency and are not in the Terrorist Screening Data Base,” according to a TSA bulletin in the report.

Lynch said a “meaningful examination of the purpose, scope and legality of this program will enable us to assess the effectiveness of the ‘Quiet Skies’ program and better ensure the protection of American civil liberties.”