BA cabin crew will go on strike for three days from 20 March and for four days from 27 March, union official have confirmed.
Unite called the walkout after talks to settle a dispute over pay and staff levels collapsed.
The union said it would not strike over Easter but warned that more action could follow after 14 April if no deal was agreed.
Steve Turner, the Unite national officer for civil aviation, said: "It is hugely concerning that BA feel that management by imposition is their preferred approach.
"Very soon, no worker at the airline will feel that either their job or their terms and conditions are safe. This instability cannot be healthy for the airline."
Up to 12,000 staff will be involved in the walkout.
The airline said in a statement: “Unite's action has no shred of justification. Cabin crew face no pay cut or reduction in terms and conditions - and remain the best rewarded in the UK airline industry.
"We are very sorry for the stress and disruption Unite’s decision will cause. We are currently considering our response to this strike threat and what action we will need to take to minimise disruption."