I may have this wrong but I read the story as :
5 aircraft have had their ducts done, but it seems only 1 aircraft of those aircraft has had fuel seals changed (is this MoD info?)
I think the MoD have implied those 5 can fly - as presumably the ducts were the Mar 09 grounding issue - hence the fuel seals are not a grounding issue -
EDIT on checking they have actually stated this explicitly - "Delays to the replacement of fuel seals will, however, have no impact on flying since our experts assess that the risk is tolerable."
The BBC has seems to have ignored this to imply that only 1 is airworthy, and stated in earlier reports that the MoD had not clarified the issue (despite the fact that I did a 10 sec search on the mod site to produce the quotes above where it seems pretty clear to me!).
Ministry of Defence | Defence News | Equipment and Logistics | Nimrods requiring safety modifications to temporarily cease flying
Hence on this occasion, the MoD appears to have had their facts completely twisted by the media to create a better story.
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This issue of timeliness in ALARP has been raised on this thread many times as another dimension to any ALARP assessment - but this continues to be misunderstood it seems by many on here.
A good example is that the 777 are still flying today with unmodified Trent 800 engines & its current Fuel Oil Heat Exchanger (FOHE) technology - the FAA have given operators around 6 months after a Rolls Royce modification is developed (so 6 month clock not even ticking yet - it will only start when Rolls have a fix) to get it fixed - until that time the risk of a heathrow crash repeat is quite real (noting the workarounds to minimise the risk). So is it ALARP? Well you can argue the aircraft is not really ALARP as you can improve the FOHE and fit it - but this hasn't been installed yet and can't practically be done for 6-12+ months. The FAA are content that there are workarounds to mitigate the hazard so are content that it is reasonable to keep flying as long as the mods are embodied within a reasonable time. Hence you could say they are working towards an ALARP build standard of the 777 fleet - this is where the terminology can get confusing, as it is also true to say the whole situation is ALARP, as the the risks have been minimised by outlining an timely upgrade plan. Hence you can say the risks to current 777 ops are ALARP, even though the new FOHE won't be fitted for months. Hope that makes sense, and the parallels to Nimrod are obvious.