Heathrow Express faces a third strike this year by workers in a dispute over cuts.
Members of the Rail, Maritime and Transport union plan to walk out for 24-hours from 3am on June 4.
The RMT claims plans to save £6 million over five years would threaten 200 jobs and affect safety.
A Heathrow Express spokesman told the BBC it ran a good service during the other walkouts and will do so again.
Half-hourly services have run between London Paddington and Heathrow rather than regular trains every 15 minutes.
RMT acting general secretary Mick Cash said: “Despite the bogus claims from the company, the fact is that the previous two phases of strike action were solidly supported by the staff and the service was reduced down to a skeleton operated by scab managers, with limited training, while Heathrow Connect was closed entirely.”
He added: “The planned axing of jobs, and the associated freezing and hacking back of pay and working conditions, is a kick in the teeth for the staff who have made Heathrow Express and Heathrow Connect the success story that they are today.”
Heathrow Express managing director Keith Greenfield said: “We have asked the RMT to suspend their action to allow constructive talks at Acas but instead the union’s leadership has decided to strike yet again – despite our making clear repeatedly that strikes are self-defeating, leading ultimately to a worse outcome, not a better one, for their members.
“That is because each strike adds to the £6 million of cost Heathrow Express needs to save over the next five years in order to secure our future and jobs for our people.”