Bus services in Aberdeen could be hit by industrial action next month.
Contract workers at First Bus depots in Glasgow and Aberdeen are set to strike in a dispute over pay.
The Unite union said more than 100 cleaners, fuellers and shunters with Bidvest Noonan would take industrial action at both depots between March 1 and 4.
More walkouts are planned at the Aberdeen depot between March 8 and 11.
Unite said the action was being taken after workers rejected a 2% pay offer from Bidvest Noonan backdated to 2022.
First Bus said it was "assisting Bidvest Noonan to find an agreement that is mutually beneficial to all".
Buses off the roads?
Unite said buses across Glasgow and Aberdeen may have to be taken off the roads for safety and recharging reasons during strike days.
Unite general secretary Sharon Graham told the BBC: "Bidvest Noonan's pay offer is totally unacceptable."
The contract workers in both cities were outsourced by First Bus in Glasgow in 2016, and then in 2020 in Aberdeen.
- Meanwhile, targeted strike action is taking place in Scotland in the row over teachers' pay.
The Educational Institute for Scotland is staging walkouts in the constituencies of some politicians.
Schools are affected in areas represented by First Minister Nicola Sturgeon, her deputy John Swinney, Education Secretary Shirley-Anne Somerville and Greens MSP Ross Greer.
Ms Somerville said she was focused on resolving the dispute.
The BBC says the union rejected a new pay offer last week.
Teachers want a 10% pay increase which ministers say is unaffordable.
The latest offer included a 6% pay rise in the current year and a further 5.5% in the new financial year.