Ryanair will add more than 500 flights to its schedule over the October half-term holiday in a bid to attract travellers after Heathrow said it would continue to limit passenger numbers.
The Dublin-based airline said the extra flights at the Essex airport will have capacity for 100,000 passengers.
Heathrow announced on Monday that the cap of 100,000 daily departing passengers it introduced in July due to staff shortages will continue until 29 October. It had been due to end on 11 September.
That will disrupt the holiday plans of many families hoping to get away during half-term - with calls growing for detail on which flights will be axed.
Aviation data company Cirium said the extension of the cap would cut capacity by more than one million seats, from 5.9 million to 4.8 million.
Ryanair chief executive Michael O’Leary said: “While hopeless Heathrow continues to cut flights and raise fares for families, Ryanair and London Stansted continue to add flights, and offer thousands of low-fare seats for the autumn mid-term break."
He added the company "looks forward to welcoming thousands of additional families".
Fares are expected to start at 29.99 euros (£25.29).
Ryanair insisted that it and Stansted have “more than sufficient staff to handle these additional flights”.
Heathrow has repeatedly criticised airlines for a shortage of ground handlers at the airport, which has resulted in thousands of items of baggage not being put on to their owners’ flights this summer.
In response to the extension of the cap, a Virgin Atlantic spokeswoman said: “We are disappointed that Heathrow Airport has already decided to extend the passenger capacity cap until the end of October, as additional resources come on line every week and the airport experience improves.
“Airline customers have a right to expect their bookings will be honoured and we’re doing everything in our power to minimise disruption, getting our customers to where they need to be smoothly.
“We urge Heathrow to provide a comprehensive plan for returning to normal operations as soon as possible.”
Heathrow was unable to provide figures on the number of people who have already booked half-term flights to and from the airport.
British Airways and Virgin Atlantic are reviewing their schedules for the period but no decisions on further cancellations have been made.
Heathrow chief commercial officer Ross Baker said: “Our primary concern is ensuring we give our passengers a reliable service when they travel.
“That’s why we introduced temporary capacity limits in July which have already improved journeys during the summer getaway.
“We want to remove the cap as soon as possible, but we can only do so when we are confident that everyone operating at the airport has the resources to deliver the service our passengers deserve.”
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