Heathrow Airport’s security, engineering and firefighting staff represented by the Unite Union will next week begin balloting for strikes, adding pressure to UK’s transport network which has been hit by a wave of industrial action.

More than 3,000 members of UK’s Unite Union will start voting on Feb. 17, with the ballot closing on March 17. These workers had rejected a 10% pay increase, the union said in an emailed statement on Sunday.

“If the workers vote for industrial action, strikes could coincide with the Easter getaway,” according to the Unite statement.

On Friday, the RMT union behind rail strikes across Britain since last summer rejected another set of pay offers. It threatened to stage more strikes “for as long as it takes.” As many as half a million workers walked out in the UK earlier this month, affecting operations across airports, ports, mainline stations and schools.