Airliners carry a variety of computer systems that could become vulnerable to hackers and U.S. regulators haven’t imposed adequate counter measures, a government watchdog report concluded.

The Federal Aviation Administration hasn’t prioritized cyber risks, developed a cybersecurity training program or conducted testing of potentially vulnerable systems, the Government Accountability Office said in a report issued Friday.

“Until FAA strengthens its oversight program, based on assessed risks, it may not be able to ensure it is providing sufficient oversight to guard against evolving cybersecurity risks facing avionics systems in commercial airplane,” the GAO report said.

Commercial aircraft carry increasingly sophisticated computer systems, including wireless networks, seat-back entertainment, position broadcasts and devices that automatically transmit data to the ground.

The FAA and planemakers such as Boeing Co. and Airbus SE have added “extensive” protections to those computers and there haven’t been any reports of successful cyber-attacks, the GAO said.

“However, the increasing connections between airplanes and other systems, combined with the evolving cyber threat landscape, could lead to increasing risks for future flight safety,” the report said.

The FAA said it agreed with five of the GAO’s six recommendations.