Health service IT systems are back online following Friday’s global outage, according to NHS England.

However, it has warned that there may still be disruption, particularly with GP services who may need time to rebook appointments.

The problems with faulty security software affected more than eight million computers worldwide, bringing chaos to transport networks and health services.

Experts have warned that the process of fixing all the computers will continue into the coming week.

In a social media post, CrowdStrike, the company whose faulty security update caused Microsoft Windows computers to crash around the world, said “a significant number” of devices that were impacted are now back online.

The NHS asked patients with appointments this week to attend as normal unless told otherwise.

“Thanks to the hard work of NHS staff throughout this incident we are hoping to keep further disruption to a minimum, however there still may be some delays as services recover, particularly with GPs needing to rebook appointments, so please bear with us,” spokesperson said.

On Sunday, the British Medical Association, which represents doctors, said GPs had been “pulling out all the stops” but would need time to catch up with lost work.

The IT outage affected the EMIS platform, which many GPs use to manage appointment bookings and patient records – including sending prescriptions to pharmacies.

The BMA said Friday had been “one of the toughest single days in recent times for GPs across England”.

“Without a clinical IT system many were forced to return to pen and paper to be able to serve their patients.”

Friday’s outage was caused by a faulty update to CrowdStrike antivirus software, which crashed Microsoft systems.

CrowdStrike CEO George Kurtz said the issue had been fixed on Friday – but admitted that it could take “some time” for some computer systems to be restored.

Though many IT systems have been fixed, other sectors are also facing some ongoing disruption.

Worldwide, the proportion of cancelled flights fell yesterday as airlines largely resumed normal operations.

According to data provider Cirium, 190 flights to and from the UK had been cancelled by 16:00 BST on Sunday. That was more than Saturday, but some were caused by other factors such as bad weather.

Europe’s largest travel group TUI said the outage was still causing delays. It cancelled 11 flights from the UK on Sunday, and said there would be a further five cancellations on Monday.

It apologised for the on-going impact of the IT outage.