The FAA might revive TCAS III. The system, which would add lateral resolution advisories (RA) to the current TCAS II’s vertical commands, was proposed many years ago but dropped after technical investigations showed that it would have been extremely difficult to develop and implement. The renewed interest in TCAS III comes from the expectation that future unmanned aerial vehicles (UAVs) operating in the National Airspace System would be unlikely to have the climb capability required in a current RA vertical avoidance maneuver. It was suggested that an AD could one day be issued to mandate an upgrade of all TCAS II units to TCAS III standards. However, several industry specialists told AIN that such a proposal would be strongly opposed by the manned aircraft community and ATC. The established position–from the International Civil Aviation Organization down–is that UAV performance limitations should not have an adverse effect on other airspace users.