Airport securityBox-cutter knives were apparently used in the September 11, 2001 Terrorist Attack, though such knives are not usually considered weapons. The hijackers could have very easily gotten these type of knives past airport security since up until the attacks, they fit the qualifications to be permitted on U.S. domestic flights: any knife with a blade up to 4 inches long was permitted. FAA rules placed into effect on September 13, 2001 prohibit any type of knife in secured airport areas and planes. Airport security for the two flights out of Newark and Washington Dulles had been provided by Argenbright Holdings Ltd, a company which had plead guilty to federal fraud charges in May 2000 because they had hired 1,300 untrained security guards, including several dozens with criminal records, at Philadelphia International Airport. The company is still on probation. Profiling on people who look Arabic was greatly stepped up after the attack.