WASHINGTON (CNN) -- When the nation's top transportation security official announced a plan to allow some small knives on planes, he spoke to a group receptive to his message: international aviation folks that already allow knives.
It may be the only receptive group.
In the week since Transportation Security Administration chief John Pistole made his announcement, a parade of groups has stepped up to voice opposition or concern.
The list is a virtual who's who of what the TSA typically calls its partners or stakeholders in aviation security.
-- The American Federation of Government Employees, a union that represents the nation's 50,000 airport screeners.
-- The Federal Law Enforcement Officers Association, a nonprofit group that represents an undisclosed number of federal air marshals.
-- The Flight Attendants Union Coalition, a group of five unions representing 90,000 flight attendants.
-- The Coalition of Airline Pilots Associations, which represents pilots.
-- U.S. Rep. Bennie Thompson of Mississippi, the senior Democrat on the House Homeland Security Committee.
-- Major airlines, represented by their trade association, have expressed concern with the policy as a group. But individually, three of the five biggest carriers -- Delta, American and US Airways -- have come out against it.
Supporters of the initiative are more difficult to find.
None of the groups that the TSA labels "stakeholders" has publicly endorsed the small-knife policy, and only a handful of policymakers, lawmakers and security experts have lent it their support.
The Air Line Pilots Association International, the nation's largest pilots union, has neither supported nor opposed the knife rule directly, saying only that it supports initiatives such as Pre-Check that "focus on the real security threats instead of objects."
Pistole's predecessor, former TSA Administrator Kip Hawley, supports the move.
"In retrospect, I should have done the same thing," Hawley told CNN.
"The air marshals and the flight attendants have legitimate concerns, certainly, for their own safety. But the threat of taking over a plane with a small, sharp instrument is zero. And I think with locked cockpit doors, the air marshals themselves, the pilots, the passengers, the screening that goes in ... you cannot necessarily prevent violence on an airplane, but that is not the TSA's mission. TSA's mission is to prevent a successful, catastrophic terrorist attack, and you cannot get a successful, catastrophic terrorist attack with a small knife or a whiffle ball bat," Hawley said.
The American Federation of Government Employees, the screener representative, voiced this concern:
"TSA has created a situation where TSOs (transportation security officers) will be required to discern the length and width of a knife blade in a very short period of time. Disagreements over the TSOs' determination as to whether the knife will be allowed through checkpoints may result in a confrontation," AFGE National President J. David Cox Sr. said in a statement.
"Far too often, TSOs are threatened and even assaulted by irate passengers at the checkpoint; this ambiguous new policy will only escalate those incidents. In addition, TSOs face possible discipline from an increasing number of checkpoint disputes surrounding the new policy."
The TSA said this week that Pistole will stick with the policy and implement it, as announced, on April 25. In the meantime, he will advocate for the change Wednesday in a meeting with flight attendants and Thursday at a hearing before the House Homeland Security Committee.