British Airways has said its passenger numbers fell during August, following a strike triggered by an industrial dispute at catering firm Gate Gourmet.
BA was forced to cancel about 700 flights due to the strike action
BA cancelled about 700 flights between 11-12 August after scores of ground staff staged a wildcat strike in support of sacked Gate Gourmet workers.
The action contributed to a 3.9% fall in passenger numbers carried in August against a year ago to 3.1 million.
However, BA said it still expected its annual revenues to grow at least 5.5%.
At the time of the strike action, industry experts said the dispute could potentially cost the airline up to £40m.
The dispute at Gate Gourmet, triggered by the company's decision to sack hundreds of staff following a dispute over working practices, has yet to be resolved.
BA has agreed an improved financial contract with the US-owned catering firm, which has been making huge losses on its Heathrow's operations.
However, this cannot be ratified until Gate Gourmet has reached a settlement with its own workers.
Talks between Gate Gourmet and unions are currently on hold while workers consider a voluntary redundancy package offered by the firm.
BA said the near 4% fall in passenger figures in August was attributable to a range of factors, not just the strike action.
Other factors included economic worries, currency fluctuations and the threat of terrorism.
Total revenue per passenger kilometre - a measure of the number of paying customers carried against the distance travelled - fell 0.7%.
Premium traffic - the same measure but applying to customers travelling in non-standard classes - fell 4.7%.
BA said its revenue forecasts for the year as a whole had been unaffected by the strike action.
It is expecting an increase in revenues of between 5.5%-6.5% in the year to next March.
"There has certainly been an impact because of the Gate Gourmet dispute and resultant action by BA staff," a BA spokeswoman said about the traffic figures.
"But we still expect our revenue levels to grow between 5.5 and 6.5% and that's what we have been saying for a while."