Heathrow faces the threat of 41 strikes over 23 days starting over the Easter long weekend.
The series of spring walkouts by members of the Unite union as part of a long-running dispute are due to start on Good Friday (April 2) and continue until April 25.
The industrial strike action will involve engineering, airside operations, landside operations, fire service, security and central terminal operations.
Each sector will be taking seven days of strikes. At least one of the sectors will be on strike on most days, the union warned.
Heathrow has contingency plans in place and does not expect significant disruption due to limits on international travel in place until at least May 15.
The ongoing row has been triggered by the union arguing that London hub has “fired and rehired” its 4,000 strong workforce – an accusation denied by Heathrow.
Workers took their ninth day of strike action last week.
Unite tabled proposals in February in an effort to resolve the dispute but claimed the airport has failed to “fully respond”.
Unite regional co-ordinating officer Wayne King said: “These strike days are avoidable, yet Heathrow is not listening.
“There is a fortnight before Unite’s spring strike offensive begins and HAL (Heathrow Airport Limited) management could still resolve this dispute if it has the will to do so.”
A Heathrow spokesperson said: “Every frontline colleague has accepted the new offer which pays above the market rate and London Living wage.
“Nobody has been fired and re-hired and indeed 48% saw no change or experienced a pay increase.
“In addition, we have also launched a business recovery incentive payment to all colleagues which offers a renumeration reward if the airport has recovered sufficiently in two years’ time.
“Despite losses of over £2 billion since the start of the pandemic, our approach has protected jobs and avoided huge swathes of compulsory redundancies.
“These strikes unnecessarily threaten further damage to the business, but nevertheless, we have activated extensive contingency plans which will keep the airport open and operating safely over strike days.”