The walkouts – which, according to data analytics firm Cirium, could impact 6,253 departures – involve security officers at Terminal Five, which is used exclusively by British Airways, and campus security guards, who are responsible for checking cargo that enters the airport.
"The strike action will undoubtedly result in severe delays and disruption to passengers across the airport but this dispute is a direct result of Heathrow Airport’s stubborn refusal to pay its workers fairly," said Unite regional coordinating officer Wayne King.
However, Heathrow said it will not let "unnecessary strikes" impact the holidays of its passengers.
"Our contingency plans will keep the airport operating as normal throughout," a spokesperson said.
"We are deploying 1,000 additional colleagues and the entire management team who will be in the terminals providing assistance to passengers over the busy Easter getaway."
Staff at Heathrow are represented by both Unite and the PCS Union and according to a Heathrow spokesperson, Unite refused an improved pay deal which PCS accepted.
"Colleagues could have an above inflation 10% pay increase backdated to 1 January and a lump sum payment of £1,150, but instead they’re left empty-handed by Unite’s actions," the spokesperson added.
"The only reason Unite refuse to take the improved offer to members is because they fear they’ll back it."
Unite general secretary Sharon Graham said: "Heathrow can afford to pay a decent pay rise to its workers. This is a wealthy company which is about to return to bumper profits.
"In recent years it’s approved an astronomical rise in salary for its chief executive and paid out dividends to shareholders worth billions.
"Yet somehow Heathrow executives seem to think it’s acceptable to offer what amounts to a real terms pay cut to its security guards and ground staff who are already on poverty pay."
Cirium said British Airways had been scheduled to operate 3,185 departures from Heathrow during the strike period, equating to nearly 650,00 seats.
However, in the last week, this figure has dropped to 3,106 departures, equating to a loss of over 12,700 seats.
