Brits hoping to fly abroad for holidays today have faced travel chaos when dozens of flights were cancelled this morning as security officers went on strike.
Around 1,400 Unite members have taken industrial action after last-ditch talks broke down on Thursday evening.
At Heathrow, the airport said its contingency plans are “working well”, although several British Airways flights have been cancelled.
Despite assurances, passengers have reported long queues getting through security.
Picket lines have been set up outside the airport and will be in place throughout the 10 days of continuous strike action, which ends at 23.59pm on Easter Sunday April 10.
The strikes involves security officers at Terminal Five, which is used exclusively by British Airways, and campus security guards who are responsible for checking all cargo that enters the airport.
Heathrow’s chief executive John Holland-Kaye told Sky News: "I'm here in Terminal Five which is the only terminal that voted for strike action and you'll see it's operating as normal.
"We have a lot of colleagues who have come to help us out today - both security officers and managers who are helping out in their purple shirts like me.
"But we also have some other agency, third party, workers who have come in to help us who are very experienced in this kind of security environment, and they're keeping the airport running smoothly.
"So, Heathrow is operating as normal. If you're travelling over the Easter period, don't worry, you'll have a good journey.”
Brits' have already been warned their holiday plans may be affected by French air traffic controllers walking out as protests continue in France over plans to raise the age of retirement.
Unite general secretary Sharon Graham said current pay offers to security and ground staff is a “real-terms pay cut” to people on “poverty pay”.
He added: “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.
"Unite has a laser-like focus on our members' jobs, pay and conditions. The workforce at Heathrow Airport will receive the union's unswerving support in this fight for a decent deal."
Unite regional co-ordinating officer Wayne King said: "Heathrow Airport has thrown away the opportunity to avoid strikes.
"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."
