Travel agents are switching flights away from British Airways (BA) and customers are asking to be booked on rival airlines as cabin crew threaten fresh strikes.

The cabin crew’s union Unite has announced more than 13,000 BA members will begin voting on whether to strike in March before the Easter holidays.

BA chief executive Willie Walsh this week wrote to all the airline’s UK ground staff asking them to train as cabin crew and work as strike breakers in the event of any action.

In December, a proposed 12-day strike by cabin crew was thwarted only after the High Court ruled the action illegal.

Travel Designers managing director Nicholas McKay said he was finding new flights with rival airlines for about 20 BA customers travelling in March who are yet to be ticketed, despite some of the flights being more expensive.

He said: “I’m thinking about customer service. A lot of our clients are getting married or going on their honeymoons: I can’t risk them being let down.”

John Allan Travel owner John Allan said he had already booked one couple going to the Maldives on alternative SriLankan Airlines flights at their request, even though it cost £300 more.

He added: “Customers want to look forward to their holiday without fear or trepidation. If people want to spend more money booking an airline other than BA, I’m with them.”

Bryton Travel managing director Bryan Bath said although he is not switch-selling customers away from the airline, he is warning them of the strike. “We have no confidence in BA and we’ve got enough going on without having to worry about dealing with the airline,” he added.