Airport cleaners have started a second seven day-strike in a dispute over pay.
The Unite union said cleaners employed by Sasse at London Luton Airport "can not make ends meet" on their wage of £7.83 an hour, adding that they do not have enough to "live on".
Sasse said it had offered staff "a 9% increase over three years", and was paying them "above the minimum wage."
The airport said it was working to minimise any effect on passengers.
The action started at 06:30 GMT and is due to end at 06:29 GMT on 28 December. A previous strike was held between 4 and 11 December.
Jeff Hodge, regional officer for Unite, said: "The cleaners are fighting against poverty pay this Christmas because Luton Airport and Sasse refuse to recognise the real hardship the workers and their families face."
"By 2021 cleaners at Luton Airport still won't be earning a real Living Wage which is the minimum that workers need to get by."
Benny Wunderlich, managing director of Sasse UK, said the company had offered staff a 9% increase over three years, "which at all time puts our employees pay above national minimum wage".
"By continuing strike action Unite are placing our employees at a detriment," he added.
"We encourage Unite and our staff to accept this offer to end the strike action."
An airport spokesman said: "Whilst we cannot comment on the dispute between Unite and Sasse, we are working hard to ensure there is no disruption to our passengers."