The unofficial strike among British Airways staff at London's Heathrow has brought chaos to thousands of passengers across the world.
More than 100 flights from Heathrow alone have been affected
Three Qantas flights from Australia to London have been diverted to Frankfurt because they have been unable to land at Heathrow.
BA says flights will not restart until 1900 GMT on Friday at the earliest.
Nearly 100 BA aircraft and 1,000 pilots and cabin crew are in the wrong places around the world, the airline says.
The three Qantas flights left Melbourne and Sydney - carrying some 1,000 passengers - bound for Heathrow as scheduled.
But as it became clear that BA ground staff - who service Qantas aircraft - were staying on strike for a second day, the flights were diverted to Germany.
Another long-haul flight currently en route could be forced to do the same, the BBC's Phil Mercer in Sydney says.
Two Qantas flights from Heathrow to Australia were cancelled on Thursday.
Some 2,000 Australia-bound passengers were stranded overnight at the London airport, the Sydney Morning Herald reports.
Sri Lankan Airways planes are also serviced by BA staff at Heathrow.
The airline's scheduled flight to London was continuing as normal but would divert to London Gatwick if the dispute remained unresolved, the airline said on its website.
"A decision whether to divert to Gatwick will be made when the aircraft enters European air space and our crew will advise you," the statement said, adding that road transport to Heathrow would be provided.
AFFECTED AIRLINE NUMBERS
British Airways: 0800 727 800
Qantas: 0870 000 0123
Sri Lankan Airlines: 0208 538 2000
Finnair: 08705 997711
GB Airways: 0870 850 9850
British Med Airlines: 0870 850 9850
Finnair - another airline that uses BA ground staff - said it had to cancel two morning flights and an early afternoon flight.
But it was waiting for advice from BA before deciding whether to cancel later flights, said Finnair spokeswoman Maria Mroue.
"At this moment we have not made alternative plans, we are waiting to see if we can fly again later on today," she told the BBC News website.
Meanwhile, passengers hoping to fly back from Malaga in Spain and Morocco's Marrakech and Casablanca with the BA franchise GB Airways were also affected.
They have been told that unless they desperately need to travel back on Friday, they should re-book on to an alternative flight.
The strike started on Thursday when BA ground staff walked out in support of sacked catering workers.