EI-WAT,
There are restrictions for the 72 in WAT when taking off from 03 and sometimes for 21 as well. A fully booked 72 to LTN and especially LRT can cause quite some problems weight wise when 03 is in use
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As for SXL both the 42 and 72 are restricted for takeoff but it's no problem for the 72 as it is rarely full when flying to DUB plus you don't need much fuel to fly back to DUB.
Tfcm