By JOAN LOWYWASHINGTON (AP) â¿¿ The head of the Transportation Security Administration told lawmakers Thursday he stands by his plan to allow passengers to carry small knives onto planes despite a growing backlash against the proposal. It's unlikely in these days of hardened cockpit doors and other preventative measures that the small folding knives could be used by terrorists to take over a plane, TSA Administrator John Pistole told a hearing of the House Homeland Security Committee. On the other hand, searching for the knives on passengers or in their carry-on bags is time consuming, Pistole said. TSA screeners confiscate about 2,000 such knives every day, with each incident chewing up about two to three minutes, he said. "I think the decision is solid and it stands and we plan to move forward," Pistole said. The policy, which goes into effect April 25, has sparked strong opposition from flight attendants, federal air marshals, some pilot unions, and even aviation insurers. In the hands of the wrong passengers, the knives can be used to harm flight attendants and other passengers, critics say. Several airline CEOs have also expressed qualms. Delta Air Lines chief executive Richard Anderson said in a letter to Pistole last week that he shares the "legitimate concerns" of the airline's flight attendants. US Airways chief Doug Parker asked the TSA administrator to reconsider his position. Several members of the House committee also urged Pistole to drop the proposal, warning that if he doesn't, Congress may take steps to block the policy change. Since the Sept. 11, 2001, terrorist attacks there have been no incidents in which terrorists have successfully used sharp objects to take over a plane, which suggests the current policy of keeping even small knives off planes is working, committee members said. "How does allowing sharp objects on board now accomplish maintaining the goal of having zero planes taken over?" asked Rep. Eric Swalwell, D-Calif. "I'm asking why now, and why do we want to go back?"