“Effective at 7:00 a.m. on Sep 22 [2001], FAA [Federal Aviation Administration] lifted some of the restrictions on general aviation (Part 91) flight training under Visual Flight Rules (VFR). Such training might be permitted in non-turbojet aircraft of less than 12,500 lbs. outside of Enhanced Class B airspace. Training in single- and twin-engine piston powered aircraft and helicopters was permitted within Enhanced Class B airspace except in and around Boston and in the areas of New York City and Washington, D.C., covered by temporary flight restrictions. Part 91 sightseeing outside of Enhanced Class B airspace and temporary restricted areas was also allowed to resume.”
– FAA, “Chronology of the September 11 Attacks and Subsequent Events Through October 24, 2001,” FAA Believed Second 9/11 Plane Heading Towards NY for Emergency Landing, The National Security Archive, Sep. 9, 2005