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The crew of the B737 was recleared from a standard level to a non-standard level and, in order to provide track shortening, from a track that would have provided separation with the B767, to one that conflicted with the B767. The allocation of a non-standard flight level on a one-way route does not guarantee separation from opposite traffic on other, crossing, one-way routes. However, the planned routes of these two aircraft did not cross and were laterally separated. The conflict would have been avoided had the B737 continued on its planned route or had it maintained a standard level.

The B767 crew was recleared to F350 after the B737 crew had already been cleared direct to ALLOC and had been assigned FL350. Had an intermediate flight level below the B737 been assigned to the B767 crew, until the aircraft passed, the conflict would have been avoided.

The ELW/BLA instructor was concentrating on the student. Neither controller realised that the B737 had entered the WOL/JVS sectors. Had the transfer of control and jurisdiction of the B737 been initiated before that aircraft crossed the boundary between the sectors, as it should have been, the WOL/JVS controller may have become aware of the imminent conflict.

The WOL/JVS controller had been distracted by a low priority task. Also the contrast on the WOL/JVS ASD may have been below specification and that possibly impaired the ability of that controller to maintain situational awareness.

Neither the WOL/JVS controller nor the ELW/BLA controller effectively employed the tools available in TAAATS to highlight the non-standard nature of the B737 flight; either the non-standard level, or the direct route. Use of a standardised method of highlighting the non-standard nature of a flight may assist controllers with conflict recognition.

When operating sectors that have been combined, diverse scenarios and increasing workloads can quickly distract controllers. Controllers need to be vigilant and recognise the need to separate sectors ahead of the requirement to do so.

All the controllers were distracted by events occurring on their ASD's away from where the conflict occurred. The instructor eventually detected the conflict using effective scanning techniques. Although scanning in this case was not done in time to avoid the conflict, it allowed for timely avoiding action. It also demonstrated the importance of effective scanning not only in conflict recognition, but in recognising when other actions are due, or over due, especially during, and after, busy periods and in larger sectors with multiple crossing points.

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