HF,
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Ground staff pen pay is same as basic pay minus the abait figure or 15% depending on NAPs 1 or 2, all other extras like shift pay are outside and do not count for pen pay.
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My understanding is the company put all flying staff extras like shift or flying pay into basic and that is why at present flying staff get pen pay on 80% of present basic pay.
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I think it is only Fair that if the company are offering a 18.75% pen pay rise to some staff, they should offer it to all, they could make it an option on changes, tick if you want it will be fine, then any flying staff who think it's a bad deal can leave the box empty, like it or not this would appear Fair and be an Equitable outcome?