11.   The planes were close enough that the on-board traffic collision avoidance system sounded an alert on the American Airlines plane.

12.   Their collision avoidance system uses radar to detect objects on the road.

13.   A collision alert system called TCAS, which warns pilots of nearby aircraft and tells them what evasive action to take, is required on commercial aircraft.

14.   In both cases, on-board collision alert systems warned the pilots, who took emergency action.

15.   Other services under development include a collision avoidance system that warns drivers of dangers when approaching an intersection or railroad crossing.

16.   The BA spokeswoman said that checks to the traffic collision avoidance system on board the British Airways jet showed it had been functioning correctly.

17.   The collision warning systems are standard on commercial aircraft.

18.   The pilots took evasive action after being alerted by onboard collision systems.