British Airways intends to operate at least 60% of longhaul flights and more than 50% of shorthaul flights from Heathrow in the first strike period, which begins on Tuesday, May 18.
BA said all flights would continue to operate out of Gatwick and London City during the cabin crew walkout over pay and working conditions.
The schedule for the second strike period, which runs from May 24-28, will be announced on Wednesday 19 May for longhaul flights and Thursday 20 May
The industrial action will last 20 days over a 23 day period, with four five-day strikes.
Customers whose flights are cancelled will be able to cancel, move to another date or transfer to a nearby destination.
According to reports, BA boss Willie Walsh has said he will permanently strip staff travel perks from any cabin crew who join the walkout.
The dates are:
May 18 to 22
May 24 to 28
May 30 to June 3
June 5 to 9