On 1 Jul 2002, a Bashkirian Airlines Tu 154 and a DHL Boeing 757 are approaching each other. Both aircraft are at 36000ft due to ATC errors.
21:34:42 Both aircraft receive TAs
21:34:49 ATC instructs Tu 154 to descend to 35000ft
21:34:56 Boeing 757 issued “Descend, descend” RA. Crew responds
21:34:56 Tu 154 issued “Climb, climb” RA. Crew continues to descend
21:35:03 ATC instructs Tu 154 to increase descent rate
21:35:10 Boeing 757 issued “Increase descent” RA. Crew responds
21:35:19 Boeing 757 advises ATC they are responding to TCAS RA
21:35:24 Tu 154 issued “Increase climb” RA. Crew continues to descend
21:35:32 Both aircraft collide overhead Überlingen
Time from first TAs to collision: 50 seconds
TCAS RAs always take priority over ATC instructions!