Washington ( CNN ) -- Small pocketknives and an array of sporting equipment -- banned from aircraft cabins in the wake of the September 11 , 2001 , terrorist attacks -- will once again be allowed in U.S. planes , the head of the Transportation Security Administration said Tuesday . Knives with blades that are 2.36 inches ( 6 centimeters ) or shorter and less than a 1/2 inch wide will be permitted on U.S. airline flights as long as the blade is not fixed or does not lock into place . Razor blades and box cutters are still not permitted . Two golf clubs , toy bats or other sports sticks -- such as ski poles , hockey sticks , lacrosse sticks or pool cues -- will also be allowed in carry-on luggage . Transportation Security Administration head John Pistole said the changes will take effect April 25 and will bring the United States into alignment with international rules . Some security experts say security improvements since the attacks -- most notably reinforced cockpit doors , better intelligence and motivated passengers -- have made the strict prohibition of small pen-knives unnecessary . Pistole said the changes are in keeping with his `` risk-based security '' initiative and will permit airport screeners to focus on looking for bomb components , which present a greater threat to aircraft , instead of lesser threats . But a union representing 90,000 flight attendants called the measure `` a poor and short-sighted decision by the TSA . '' `` Continued prohibition of these items is an integral layer in making our aviation system secure and must remain in place , '' according to a statement by the Coalition of Flight Attendant Unions . Although it was widely reported that the 9/11 hijackers used `` boxcutters '' in their attack , the weapons were not recovered , and investigators believe other types of knives were used . At a January 2004 hearing of the 9/11 Commission , a commission staff member said , `` Our best working hypothesis is that a number of the hijackers were carrying -- permissible under the regulations in place at the time -- permissible utility knives or pocket knives . '' The commission displayed a Leatherman knife , saying , `` We know that at least two knives like this were actually purchased by the hijackers and have not been found in the belongings the hijackers left behind . '' Immediately after the attacks , the TSA prohibited a wide range of items from aircraft , but it has gradually been reintroducing some banned items such as cigarette lighters and matches . On occasion , such as a liquid bomb scare in August 2006 , the TSA has expanded the list , banning large containers of liquids and gels . Under the TSA 's risk-based security , Pistole has sought to `` reduce the haystack , '' giving modified screening to travelers under age 12 and over age 75 . It has also expanded its TSA PreCheck initiative , which expedites checks of known passengers . TSA spokesman David Castelveter said the changes announced Tuesday will not slow down the screening process by requiring screeners to measure knife blades and weigh plastic bats . Screeners will use `` common sense '' when applying the rule , he said . A major pilot 's union on Tuesday declined to comment on the specific changes announced by the TSA , saying it had not had time to study them . But it applauded the TSA 's efforts to harmonize U.S. rules with those overseas , and its embrace of risk-based security . `` Unfortunately , the reality has been that we 've had this patchwork of regulations and systems that in some part ... have been carried on the shoulders of the airlines , '' said Capt . Sean Cassidy , first vice president of the Air Line Pilots Association International . Cassidy said risk-based security benefits the industry , the airlines and travelers .
The TSA did ban certain knives and other equipment on planes . Better security , such as reinforced steel doors , allow for the change . A flight controllers ' union says the bans should have remained .