The FAA has withdrawn its decade-old proposal to rescind its requirement for Mode-S transponders and adopted a new rule that will end the hundreds of Mode-S installation exemptions currently in effect. Beginning March 1, 2007, Part 121 and 135 operators will no longer be exempted to fly without a Mode-S transponder. No new exemptions will be granted after that date, though Mode-A or -C transponders can continue to be used until they can no longer be repaired, after which they would have to be replaced with a permanent Mode-S unit. When the FAA in 1996 proposed to rescind the mandate to install Mode-S transponders (except on aircraft equipped with TCAS II), the agency was inundated with requests for exemptions, as operators anticipated the Mode-S requirement would be withdrawn.