The photo has been used for illustrative purposes only.
Reports suggested at least 18,000 passengers were grounded after the services in and out of Gatwick and Heathrow — Britain's busiest airports – were cancelled.
More than 200 other BA flights were delayed, according to the BBC. The airline declined to give a number of flights affected.
BA blamed "a systems issue which has resulted in some short-haul cancellations and delays from London airports".
A display warns passengers to "Expect Disruption" to British Airways flights at Heathrow Airport. AFP
It later said the issue had been resolved, and apologised to affected passengers.
"Our teams have been working tirelessly to get the vast majority of customers on their way, with most of our flights departing," it said.
"Our flights are returning to normal, however there may be some knock-on operational disruption as a result of the issue earlier."
BA had offered customers booked to travel Wednesday on short-haul flights departing from Heathrow, Gatwick and London City airports the chance to rebook to travel on another day between Aug.8-13.
Frustrated passengers took to social media to vent their anger and demand answers from BA, while some shared photos showing airport terminals filled with stranded travellers.
"There is no staff at the airport, we're in an info queue that isn't moving," Anya, a BA passenger bound for Zagreb, Croatia, tweeted.
"The only staff around are the duty free staff and they've been more helpful than anyone at BA. Get your act together #britishairways!"
A Heathrow spokesperson said BA was experiencing "a technical issue with its systems" impacting check-in and departures there.
The disruption is the latest incident to impact British Airways in recent years.
A 2017 worldwide system outage affected tens of thousands of its passengers, while a 2018 cyber attack saw hundreds of thousands of customers' personal data stolen.
The UK flag carrier and its 4,300 pilots have been locked in a nine-month pay dispute that could disrupt the travel plans of nearly 300,000 people.
The Ufo labour union on Friday announced strikes from Monday to Wednesday this week at Germanwings, which operates on behalf of Lufthansa's Eurowings brand, saying little progress has been achieved in talks with Lufthansa management.
The PIA spokesperson Abdullah Khan told media that the Pakistani government granted permission for the chartered flight on humanitarian grounds after a passenger hailing from Gujrat requested the authorities.
Emirates Airlines has suspended passenger flights from India effective April 24 until June 30, 2021, according to a statement on its website. Furthermore, passengers who have transited through India in the last 14 days will also not be accepted to travel from any other point to the UAE.
UAE's Embassy in London welcomed over 500 friends from the UK, UAE, and internationally to a grand reception at London’s famed Natural History Museum in South Kensington to commemorate 51 years since the founding of the UAE.
"On this day, we commemorate the bright memory of the Founding Fathers, led by the late Sheikh Zayed Bin Sultan Al Nahyan, and his brothers, the Founders of the Nation, as well as their determination, wisdom and vision that established the Union.”
President His Highness Sheikh Mohamed Bin Zayed Al Nahyan said that the 51st UAE National Day is a day to recall lessons of the past, and look at the present with awareness and contemplation, while looking to the future with hope, optimism and confidence.