London, England (CNN) -- British Airways was able to get three out of four planes to their destination this weekend despite the ongoing strike by cabin crew, the airline's CEO, Willie Walsh, said Sunday.





Walsh told CNN he was "clearly disappointed for customers who have had disrupted travel plans but I'm really pleased that we have been able to do so much and we are determined to keep this going.





"We have had high numbers of cabin crew turning up for work. We wouldn't have been able to fly such a significant operation if we didn't have cabin crew supporting us," he said.





But the assistant general secretary of the Unite union, which represents the cabin crew, said BA was losing money and shifting customers onto other airlines in a "con trick."





Are you worried about the strike?





"BA is claiming that it can function but it is doing so by throwing away millions of pounds every day as it dumps its passengers on other carriers," Unite's Len McClusky said in a statement.





"Passengers who turn up expecting to fly BA, a brand they trust and have paid a premium for, will now be shipped onto carriers they've never heard of."





British Airways and Unite have been at odds for more than a year over changes the airline wants to make to cabin crew pay and work practices.





BA says the changes will save the company more than 60 million pounds ($90 million) a year. Unite has said the plans, which call for longer work hours and less staffing, will damage customer service and the BA brand.





At least 51 British Airways flights leaving Heathrow Sunday were listed as canceled on the airport's Web site, and at least 79 arrivals were listed as canceled, as of 10:30 local time (5:30 a.m. ET).





Destinations in the UK, United States, Europe, Africa and the Middle East were directly affected by the cancellation of BA flights. And other airlines such as American Airlines, Cathay Pacific and Iberia were showing flight cancellations because of code-sharing.





The union claimed half of British Airways flights were canceled on Sunday. BA in the past has said it is legally bound as a publicly traded company to provide accurate information, while the union is under no such obligations.





The latest strike, which began Saturday, meant American student Brittany Smith and her family were being rerouted from London's Heathrow to Atlanta, Georgia, on their way home to Denver, Colorado.





She has already e-mailed her professors to explain that she will not make class. "It is frustrating, but if you let it frustrate you, you're just going to ruin your travel plans even more," she told CNN.





"So you are just going to have to take it with a grain of salt, and realize that everyone is doing the best they can and to make it easier on everyone to stay positive."





The four-day strike is the union's second one in a month over pay and working conditions. It staged a three-day walkout last weekend





BA said its operations got off to a good start Saturday despite the strike by thousands of its cabin crew members.





The airline said it was able to operate flights as normal at two London airports, Gatwick and City, and that the number of crew members reporting for work at Heathrow was enough to operate BA's planned schedule.





It said enough staff had crossed the picket lines that it was able to fly more than 75 percent of customers scheduled to travel during the strike. Another 18 percent of passengers are booked to fly on other carriers or have changed their travel dates to avoid the strike, the airline said.





Advice for passengers





The Unite union, which represents 95 percent of BA's 15,000 cabin crew, said it was too early say how many crew members worked despite the strike.





The airline said it will be able to run a full operation from London's Gatwick and City airports.





At London's Heathrow Airport, BA will be able to run up to 55
Who's been fighting? What is the labor dispute over? What was canceled? What's the percentage of flyers? What did British Airways say?
British Airways and Unite changes the airline wants to make to cabin crew pay and work practices. half of British Airways flights 75 percent "clearly disappointed for customers who have had disrupted travel plans
question: Who's been fighting?, answer: British Airways and Unite | question: What is the labor dispute over?, answer: changes the airline wants to make to cabin crew pay and work practices. | question: What was canceled?, answer: half of British Airways flights | question: What's the percentage of flyers?, answer: 75 percent | question: What did British Airways say?, answer: "clearly disappointed for customers who have had disrupted travel plans