The strikes, scheduled for May 4-6, 9-10 and 25-27, follow a 10-day walkout by security staff that ended earlier this month.
Unite said the strikes will cause “inevitable disruption and delays” at a time when people are expected to be travelling to the UK for the King’s coronation on May 6.
However Heathrow Airport insisted that services will run smoothly during the fresh wave of strikes.
It comes as traffic wardens in Westminster are to strike on the day of the King’s coronation in a dispute over pay and conditions.
MNA/PR