Perhaps I don't see the problem correctly? A bunch of people who are in a final salary pension scheme are striking because the scheme has been closed to new starters ie people who don't yet work for BAA
Normally when this sort of thing happens, the problems stem from lack of funding for the future.
If at any time, the "pension pot" was to fall below the level required to pay out all the current pensioners, the administrators have to make changes.
These can involve many things such as increasing the contributions of both employees and employees, and lowering the future expected payout for current members.
If there are no new members joining the pension scheme (normally new members would have to pay in for a few years before being entitled to a pension), the money getting paid into the scheme would fall.
This would then put a bigger burden on the current members.
Only my opinion, but this could be one cause for the upset staff.
A strike may not be pointless, due to BAA having such a monopoly, and as such, any strike will have a great deal of effect.