An FAA guidance letter has stirred debate over through-the-fence operations at general aviation airports. With security a prime concern, the agency is discouraging airport operators from allowing aircraft to taxi on and off airport property. "Airport sponsors have no federal obligation to provide airport access to off-airport enterprises or individuals," says the FAA guidance, which is open for public comment through Dec. 21. "In fact, the sponsor may simply deny TTF access if it chooses." But a new group called ThoughTheFence.org is blasting the FAA's "wholesale directive," issued just weeks after the agency vowed to evaluate projects on a case-by-case basis.