The strikes are part of a spiralling number, including railway workers and nurses to ambulance drivers and teachers.
The PCS members are expected to take part in the work at Britain's busiest airports - London Heathrow and London Gatwick - as well as Birmingham, Cardiff, Manchester and Glasgow.
The seaport of Newhaven, southeast England, will also be affected.
Prime Minister Rishi Sunak hit out at unreasonable union leaders earlier in the day and warned of new tough laws to protect the lives and livelihoods of the British public.
He did not elaborate but appeared to be referring to proposals first put forward in 2019 for a minimum level of service during strikes.
Sunak said later that work on the plan was taking place at speed. He told reporters that he would consider all ways of curbing further action, including legislation.