Delta CEO criticizes move allowing small knives on airplanes March 9, 2013 -- Updated 0236 GMT (1036 HKT) NEW: A flight attendants union president says the move "makes no sense" The TSA said it would allow small knives onto planes, starting April 25 The agency's chief says this brings the U.S. in compliance with world norms Delta's CEO says the move isn't worth the added risk to airline staff and passengers (CNN) -- Delta Air Lines CEO Richard Anderson said Friday he objects to the federal Transportation Security Administration's move this week to allow small pocketknives on airplanes. "These items have been banned for more than 11 years and will add little value to the customer security process flow in relation to the additional risk for our cabin staff and customers," Anderson said in a letter to the head of the TSA. TSA Administrator John Pistole said the move brings the United States into alignment with international rules and are keeping with his "risk-based security" approach. Under the new rules, knives with blades no longer than 2.36 inches (6 centimeters) and less than a half-inch wide will be allowed in airline cabins as long as the blade is retractable and does not lock into place. Razorblades and box cutters are still prohibited. Kip Hawley, who oversaw the TSA from 2005 to 2009, said the search for knives interferes with the search for objects such as bombs and toxins that can threaten aircraft. But others have sharply criticized the change, which was announced this week. They include the Flight Attendants Union Coalition, a nearly 90,000-member group that has launched a campaign to reverse the TSA's decision. Former flight attendant Tiffany Hawk is "stupefied" by the move, "especially since the process that turns checkpoints into maddening logjams -- removing shoes, liquids and computers -- remains unchanged," she wrote in an opinion column for CNN. And Veda Shook, president of the Association of Flight Attendants, said the move is "completely unnecessary" and "makes no sense." Rather than freeing up time, she predicted that security officers will get more bogged down testing and measuring the knives to see if they meet the criteria. How big is this knife? is it long enough? is it wide enough? Does it lock? Does it not lock? That is going to create confusion at the checkpoint," Shook told CNN's Anderson Cooper on Friday night. ..." We're all better off, and we're all safer, without weapons on board the aircraft. The Delta chief is among those critical voices, saying that he and his airline's flight attendants "share (the same) legitimate concerns." "If the purpose is to increase security checkpoint flow, there are much more effective steps we can take together to streamline the security checkpoints with risk-based screening mechanisms," Anderson said. CNN's Joe Sutton contributed to this report.