Rather than call a conventional strike, the sick-in is a good way to strike without striking. Sick-ins involve organising workers to call in sick simultaneously.
The idea is to cripple your workplace by having all or most of the workers call in sick on the same day or days. Unlike the formal walkout, it can be used effectively by single departments and work areas, and can often be successfully used even without a formal union organisation.
It is the traditional method of direct action for public employee unions in the United States, which are legally prevented from striking.
At a New England mental hospital, just the thought of a sick-in got results. A shop steward, talking to a supervisor about a fired union member, casually mentioned that there was a lot of flu going around, and wouldn't it be too bad if there weren't enough healthy people to staff the wards.
At the same time - completely by coincidence, of course - dozens of people were calling the personnel office to see how much sick time they had left. The supervisor got the message, and the union member was rehired.
In Denmark in 2006, 100 pilots went on sick-in in solidarity with striking pilots, and in 1969, thousands of American air traffic controllers went on sick-out for better conditions and wages.
Edited by libcom from an article by the Industrial Workers of the World