NATS is a profitable and basically healthy company but only just. The current financial structure was tested under most foreseeable circumstances and NATS can survive normal market down turns although not all its staff will. There are however two circumstances which the company itself may not survive. The first is a huge hike in pension costs and the second is industrial action.
You may not believe the first is a risk at all and nobody knows for sure if it would ever happen but for people supposedly versed in risk management there is a lot of ignorance here. The hazard (losing our pensions) is so great that even if the likelihood is very low it may still be in our interests to do something to mitigate it further. The possible loss of pension which will only happen if we get really big pay rises may be quite a small price to pay to reduce the risk of losing the pension altogether.
The second is entirely in our control. However if we vote No and the company imposes the deal, which it almost certainly will, then our only alternative to industrial action is a strongly worded letter.