Leaders of British Airways cabin crew have warned of further strikes after Easter unless there is a breakthrough in a bitter row over cuts which sparked more industrial action this weekend.
Unite and the airline have clashed again over the impact of a four-day walkout, with the company insisting it was flying an increased schedule, with flights full of Easter holidaymakers.
The union claimed six Heathrow flights were loaded with passengers then unloaded because of lack of crew and said many long-haul services were leaving 30% below capacity.
National officer Steve Turner warned that further strike action is likely after Easter unless an agreement is reached in the coming weeks.
Unite also announced it is seeking legal advice on BA's plans to define crew who are sick as strikers, withdrawing their travel perks as well as the concessions taken away from cabin crew who joined last weekend's walkout.
The strike will end on Tuesday night and Unite has said no further action will be taken before April 14, giving a window of opportunity for fresh talks.
A BA spokesman said: "At Heathrow we are flying our increased schedule and dozens of flights have departed, many very full with customers looking forward to their Easter holidays. The numbers of cabin crew reporting at Heathrow are currently at the levels we need to operate our published schedule.
"Our operations at Gatwick, where we aim to fly our entire normal schedule, continue to be exceptional with a large number of flights departing early. Cabin crew are continuing to report as normal at Gatwick, just as they did last weekend during the first strike period. "
Unite said most BA flights leaving Heathrow Terminal 5 had been leased from other companies, a claim the company denied. Unite said it believed BA was grounding its own flights so it could use pilots as cabin crew on other BA flights.
Len McCluskey, Unite assistant general secretary, said: "This is the great BA con trick. It's a three-card trick Paul Daniels would be proud of."