B757-200
Air Traffic Control Fully Certified
Situational Awareness; Communication Breakdown; Workload
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Human Factors; Procedure
OJT was being conducted at the sector and we were just put into hold when we took the sector. The reason we were put into a 'no notice hold' was because an air carrier departure was squawking hijack. Then the same aircraft squawked radio failure. This allowed the airport to open again. A soon as we started clearing our holding stack in they put us back into a no notice hold because fighter jets were being scrambled to escort the air carrier. This caused a big snowball effect because not only was Approach not accepting arrivals they also gave us a no notice hold for other arrivals. Right as the snowball started I had to take the frequency from the trainee because the situation was to complex for his level of training. Add to this; a couple of diversions were announced because they couldn't hold anymore. During this time is when I had a B757 lander holding over ABCDE at 150 and I had a B737 descending on the arrival going to another airport crossing FGHIJ at 130. This caused the conflict between the two. I told the B737 to stop his descent and to fly heading 180 and I told the B757 to descend to 140 expedite down and also turned him to a 270 heading. I turned both away from each other. We need to have better communication between Approach and the Center. If you know you are going to accept arrivals again you have got to be 100% sure that you can. If that takes waiting an extra five minutes then that is what has to happen. The no notice holds numerous times within a few minutes doesn't make this job any easier.
Enroute Controller described an aircraft security event resulting from an air carrier squawking the hijack code followed by the no radio code; all leading to several 'no notice' hold instructions.