LONDON (Reuters) - Air passengers in Britain and beyond faced delays on Tuesday after a “Black Lives Matter” protest on a runway halted flights for six hours at London City Airport and a computer glitch hit British Airways in London and the United States.

More than 120 flights were canceled, delayed or diverted at City, a few miles east of the Canary Wharf financial district, after nine protesters locked themselves together on the runway. Police said late on Tuesday morning they had arrested all nine and the airline was preparing to resume flights.

British Airways said it was taking longer than normal to process customers at a number of airports around the world, including London’s Heathrow and Gatwick, and urged passengers to check in online before they reached the airport.

The airline, owned by International Consolidated Airlines Group, apologized to customers.

“Really unhappy with @British_Airways “The system is down” & can’t check in!,” one passenger, Shail, said on Twitter.

Analysts at Royal Bank of Canada said the delays - the second problem with the service this year - could damage the airline’s reputation after passengers took to social media to complain about delays in San Francisco, Washington D.C. and Atlanta on Monday night.

British Airways has been rolling out a new check-in system since last year and a spokeswoman said the check-in delays were teething problems that affected many airports.

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Shares in BA’s owner rose 1.5 percent, apparently unaffected by its airline’s computer troubles.

At City Airport, the protesters earlier erected two large posters with the slogans “Black Lives Matter” and “Climate Crisis is a Racist Crisis.”

The British arm of the group, which started in the United States as a reaction to fatal shootings of black people by police, said it wanted to highlight Britain’s environmental impact on the lives of black people locally and globally. Members blocked a main road to London’s Heathrow Airport in August.

“Black people are the first to die, not the first to fly, in this racist climate crisis,” the group said in a statement.

“When black people in Britain are 28 percent more likely to be exposed to air pollution than their white counterparts, we know that environmental inequality is a racist crisis.”

The campaign group said City airport was designed for the wealthy while those who lived near the site struggled on low salaries.

Police said the protesters were now in police custody after being arrested on suspicion of aggravated trespass, being unlawfully airside and breaching London City Airport bylaws.