Unions representing nearly 50 commercial airlines are protesting federal legislation to study the idea of putting cargo planes in the hands of only one pilot with the help of remote-control pilots on the ground. But the dispute includes a mystery: officials of pilots unions do not know who put the language in the Federal Aviation Administration funding bill to study the idea of only having one pilot per cargo plane, or why it is there. The FAA bill sets aside US$128.5 million to research the concept and other research topics. Unions representing more than 100,000 pilots say they oppose the idea of eliminating a co-pilot from a commercial cargo plane because the task of flying a jet, communicating with air traffic controllers and monitoring weather changes requires two trained pilots. The unions also say remote-control flying is vulnerable to glitches and computer hackers. “Anything less than two pilots physically in the cockpit will significantly increase risk, especially during emergency operations, when timely actions are coordinated and implemented by each crew member based on real-time information,” said Robert Travis, president of the Independent Pilots Association, the collective bargaining unit for UPS. The FAA funding package for 2017-18, adopted by Congress in April, includes a line that says: “The FAA, in consultation with Nasa and other relevant agencies, shall establish a research and development programme in support of single-piloted cargo aircraft assisted with remote piloting and computer piloting.” The legislation does not explain the motivation for the study. Kara Deniz, spokeswoman for the International Brotherhood of Teamsters, which represents pilots for Aloha Air Cargo and Southern Air Cargo among other carriers, said the union does not know who put the language in the FAA bill but suspects that the study is the first step toward proposing requiring only one pilot on commercial passenger airlines. “It’s possible that this is the way to get the camel’s nose under the tent,” she said. Representatives of FedEx and Atlas Air, two of the nation’s biggest cargo airlines, declined to comment.