A federal watchdog agency says safety regulators aren’t doing enough to protect airliners from cyberattacks. The Government Accountability Office said Friday that more testing is needed to protect computer systems on passenger airplanes from hackers. Those systems are used for many purposes including communicating with pilots. The systems could be vulnerable because they transmit data from planes to people on the ground such as airline maintenance crews. The GAO says aircraft makers have built safeguards into their planes, and there have been no reports of successful hacker attacks. The Federal Aviation Administration says it agrees with most of the GAO recommendations for improvement.