Flight delays and cancellations are among the disruption expected to continue into the weekend after a global IT outage, as experts warned it could take weeks for systems to fully recover.

A flawed update rolled out by cybersecurity firm CrowdStrike knocked many offline around the world on Friday, causing flight and train cancellations and crippling some healthcare systems.

A fix was deployed for a bug in the update, which affected Microsoft Windows PCs, on Friday afternoon, with the chief executive of the company at the centre of the outage warning it would take “some time” for systems to be fully restored.

George Kurtz also apologised for events, saying he is “deeply sorry”, and made clear it was “not a security or cyber incident”.

In a technical statement, CrimeStrike said a “sensor configuration” had “triggered a logic error” which the company said had been corrected.

READ MORE: Global IT outage could last for 'some time' as problems continues around the world

Airports across the UK stressed that passengers should check with airlines for any delays or cancellations before travelling over the weekend.

Some 167 flights scheduled to depart UK airports were axed on Friday, with others delayed, while 171 flights due to land in the UK were cancelled, following the technical glitch.

Aviation analytics company Cirium said 5,078 flights – or 4.6% of those scheduled – were cancelled globally on Friday, including the 167 UK departures.

Away from travel, the National Pharmacy Association warned disruption to pharmacy services is likely to continue through the weekend, even when systems are back online, as outlets deal with a backlog of medicine deliveries.

Industry expert Adam Leon Smith of BCS, the Chartered Institute for IT, warned that it could even take “weeks” for all computers and systems to be fully restored.

“The fix will have to be applied to many computers around the world. So if computers are getting blue screens and endless loops, it could be more difficult and take days and weeks,” he said.

Professor Ciaran Martin, the founding chief executive of the National Cyber Security Centre (NCSC), also said it was hard to estimate how long it would take to recover from the outage.

“The underlying problem is fixed and the fixes are being implemented,” he said.