Journeys may still face delays and cancellations, and several airports have advised passengers to check for potential disruptions before traveling.

The outages occurred on one of the year’s busiest days, coinciding with the start of summer break for many schools in England and Wales.

GPs, pharmacies, banks, payment systems, and train services were also impacted.

The issues were caused by a faulty software update for Microsoft Windows from cybersecurity firm CrowdStrike.

In an interview with BBC Radio 4’s Today program, computer scientist Sir Nigel Shadbolt remarked that most IT systems, such as those used by CrowdStrike, typically maintain “very high levels of quality.” However, when failures occur, they can be widespread, akin to a pandemic, he noted, suggesting that lessons should be learned and advocating for the use of multiple systems to mitigate such issues.

In a blog post on Saturday, CrowdStrike CEO George Kurtz apologized, acknowledging the serious impact of the situation and expressing understanding of its gravity.

London Heathrow resumed normal operations with increased passenger traffic as those affected on Friday continued their journeys over the weekend. London Gatwick reported that while its systems were functioning normally, some delays and cancellations might persist in the coming days. Manchester Airport, where check-in was manually handled for a time on Friday, stated that its systems were operational but flights could still face delays and cancellations. Belfast International confirmed normal operations but advised passengers to stay in touch with their airlines.

The Port of Dover, free of IT issues on Saturday morning, experienced a surge of travelers who had been unable to fly on Friday, leading to a two-and-a-half-hour wait, according to ferry operator DFDS.

By Friday evening, 338 flights to and from the UK—167 departures and 171 arrivals—had been cancelled, as reported by aviation analytics firm Cirium. Simon Calder, travel correspondent for the Independent, described the situation as “horrible” for travelers and noted that many British travelers found themselves unexpectedly stranded.

Delayed and cancelled flights often have cascading effects, as planes and crews are misplaced from their scheduled positions. On the rail network, National Rail indicated that the issue no longer impacted operators, though some still advised checking journeys before traveling.

Retailers, including Morrisons and Waitrose, faced difficulties with card payments due to the outages, and TV channel Sky News briefly went off air. GPs struggled with access to their records and online booking systems, while pharmacy services and prescription access were also disrupted.

Mr. Kurtz expressed deep regret for the inconvenience and disruption caused by the outages, emphasizing that they were not the result of a security breach or cyber attack. He assured customers in an open letter of his commitment to full transparency regarding the incident and the measures being taken to prevent future occurrences.