When could a strike begin?
The earliest date at which industrial action could start is in a week's time - Thursday, 19 August.
However, some commentators have suggested that the Unite union may prefer to target the August Bank Holiday weekend that starts on Saturday, 28 August.
What are the chances of the strike going ahead?
BAA says that no union action has ever completely closed its airports in the past.
In the last planned walkout in 2002, action was called off at the last moment when an improved offer was made.