Whether the removal of staff travel was a punitive action depends on how you view the sequence of events.
The initial strike ballot took place in November 2009. BA was successful in getting a high court injunction that ruled the ballot as being void. In January 2010 Unite then announced that they intended to go forward with a new ballot, at a time yet to be determined. At that point BA stated that a direct consequence of going on strike would be the permanent removal of staff travel benefits. So before any ballot took place, the workforce had been advised that anyone who went on strike was kissing goodbye to this perk. Now it could be argued that BA were attempting to dissuade union memebrs from voting for strike action. The alternative view is that perks are there to reward the workforce and clearly, if a group of workers act in a way calculated to hit the profitability of the company, then they should have any perks removed.
What happened next is well established. The cabin crew members voted for strike action, a number of them did walk out and, surprise, surprise, did have their travel benefits removed. Howls of indignation. Did they think that it was an empty threat ? Did they not see that by walking out, they were going to cost the company money ? Of course they did. The trouble is that the cabin crew expected BA management to crumble at the eleventh hour and give in to the union demands. It didn't happen. In fact the more Unite and BASSA turned down offers made by BA, the poorer the offers became. Why ? Because it is manifestly unfair to penalise other sectors of the business simply because the cabin crew representatives were unwilling to countenance the changes in working practices being put forward.
If BA had not warned cabin crew up front what it intended to do if a strike took place,but had withdrawn staff travel after the industrial action had commenced, then it would be seen as punitive action, but the very fact that staff were warned well in advance meant that they acted in full knowledge of the consequences. Thus it was not punitive but consequential.