- Ryanair CEO Michael O'Leary called for the UK air traffic control boss to resign after flight chaos.
- Over 500 flights were delayed at London Gatwick and Heathrow due to bad weather and staff shortages.
- On Tuesday, London Gatwick Airport's CEO backed ATC chief Michael Rolfe to improve standards.
Ryanair CEO Michael O'Leary has called for the boss of UK air traffic control to resign in the wake of flight chaos.
More than 45% of flights out of London Gatwick and London Heathrow Airports — totalling over 500 — were delayed on Sunday, according to FlightAware data.
At Gatwick, where Ryanair operates some flights, 57 flights were canceled, per FlightAware.
Sunday saw bad weather in London but there were also staff shortages in air traffic control.
O'Leary blamed Michael Rolfe, the CEO of NATS, which provides air traffic control services in the UK.
"This is the latest in a long line of cock-ups by UK NATS, which has yet again disrupted multiple flights and thousands of passengers at Gatwick," the Ryanair boss said. "Airlines and passengers deserve better."
He added, "Ryanair again calls on UK NATS chief executive Martin Rolfe to step down and allow someone competent to run an efficient UK ATC service, which airlines and passengers are entitled to expect."
NATS did not immediately respond to a request for comment from Business Insider on O'Leary's remarks.
It's not the first time the outspoken boss of Europe's busiest airline has publicly criticized Rolfe.
After air traffic controller shortages during a national holiday last summer, O'Leary called for Rolfe to step down. In a statement, he referred to the regulator's report that 700,000 passengers were disrupted.
At a Tuesday press conference with Wizz Air, the CEO of London Gatwick Airport also answered questions about NATS.
"I can assure you that step by step, they're getting stronger," Stewart Wingate said.
"I remain confident that they will overall deliver very good levels of service, but will not rest until they offer seamless service to ourselves, our airlines and our passengers," he added.
A NATS spokesperson told the BBC: "We are very sorry for [Sunday's] disruption which was also disappointing for our highly professional Gatwick team, who are doing all they can to provide a seamless 24/7 service."
They added that when Gatwick appointed the organization to improve ATC performance, "everyone knew we had inherited a staff shortage that would take time to fix."