Members of a British Airways cabin crew union began a second five-day strike on Sunday after talks held last week aimed at resolving the long-running dispute ended without agreement. The new wave of industrial action by the airline's cabin staff started officially at midnight (2300 GMT) with little sign on the horizon of a breakthrough in the increasingly bitter row.
Thousands of passengers face more disruption at the start of a week of school holidays in Britain. Cabin staff are due to begin a third wave of strikes on June 5, days before the start of the World Cup soccer tournament in South Africa.
The two sides are locked in disagreement over pay, reduced staffing levels and cuts to benefits.
Talks between BA and the airline's largest cabin crew union, Unite, broke off without a deal on Friday. Conciliation service Acas said it was seeking to arrange further talks.
Seven days of walkouts in March cost BA 43 million pounds ($62 million).
The stoppages come at a difficult time for BA, which last week reported a second straight year of record losses and is battling a global economic downturn and industry-wide recession.
Continued industrial action, coupled with further disruption to flights in April caused by ash from an Icelandic volcano, could scupper BA's chances of avoiding a third year of losses.
BA Chief Executive Willie Walsh and union leaders continually blame each other for breakdowns in the often acrimonious negotiations.
On Saturday, Derek Simpson, joint general secretary of Unite, repeated his offer to suspend the walkouts if the airline restored travel perks stripped from striking crew.
The issue of travel allowances is a major sticking point in the conflict. Both sides also disagree on the impact of the strikes so far.
Despite the new strike BA said it will increase flights because more crew were returning to work than had been expected.
It said it would up its longhaul service at London's Heathrow airport to more than 70 percent of flights, from 60 percent this week. It also said it aims to increase shorthaul flights at Heathrow to 55 percent of flights from 50 percent and operate a full schedule from London's Gatwick and City airports.
BA, which flies around 90,000 passengers a day, said about a quarter of its passengers would be affected by the strikes, but that they could claim a full refund, rebook or reroute their journey.