The FAA has withdrawn a decade-old proposal to rescind its requirement for mode-S transponders and, consequently, plans to end the hundreds of mode-S installation exemptions currently in effect for Part 121 and 135 operators. It will not grant new exemptions after March 1, 2007, though mode-A or -C transponders could continue to be used in exempt aircraft until they can no longer be repaired, after which they would have to be replaced with a mode-S unit. When the FAA in 1996 proposed to rescind the mandate to install mode-S transponders (except on aircraft with TCAS II), the agency was inundated with requests for exemptions, as operators anticipated the mode-S requirement would be withdrawn.