Prospect members will start voting in early March, on action which could take place as soon as the Easter weekend. The action will take many forms and will result in airport closures and flight cancellations if members vote yes.    

Alan Denney, Prospect national secretary, said: “It is entirely unacceptable to our members that Scottish Ministers are permitting this level of discrimination between workers in the same government-owned business to continue”.

“The unequal employment conditions that prevail are contrary to the concept of “fair work” endorsed by first minister Nicola Sturgeon, who on appointment introduced a cabinet secretary post to deliver this commitment.

Despite AMSL merging with HIAL six years ago, workers are still receiving inferior terms for work of equal value. This includes basic pay, sick pay, shift pay, weekend premium payments, overtime, and annual leave allowances.

Prospect is seeking an end to these unjustified inequalities across the board, including in sick pay, where AMSL members receive just five half days per annum, in contrast to six months’ full pay – in simple terms – for the staff who manage these members, and other colleagues in the wider group.

The union claim includes a 5% increase in the basic rate of pay and across airport equality for AMSL’s 160 workers, raising minimum pay levels to £10 per hour for those who keep passengers safe when they fly.

Prospect is now calling on the Scottish government, and Roseanna Cunningham, the fair work secretary, to take responsibility and intervene to avoid a potential extended period of airport disruption or closure.