The airport was forced to cancel more than 60 flights on Monday as it struggled to cope with the rebound in travel demand after the swine flu.
British Airways, Virgin Atlantic and Air France were some of the airlines affected by the flights.
More passengers are expected in Terminals 3 and 5 today than the airport currently has capacity to serve, so we have asked some airlines in Terminals 3 and 5 to remove a combined total of 61 flights from the schedule.
We apologize for the impact to travel plans and we are working with airlines to rebook passengers on other flights.
Frequent delays at security, lost baggage, and the failure to send staff to help travellers with mobility issues have been reported by passengers at many airports.
In the month of June, 6 million passengers traveled through the airport, the equivalent of 40 years of growth in just four months. The total number of passengers was 19.4 million.
There have been periods in recent weeks where service levels have not been acceptable with long queue times, bags not travelling with passengers or arriving late, and we want to apologize to any passengers who have been affected by this.
After the UK government pushed a "slot amnesty" to allow carriers to cancel flights without losing access to airports, it said it would "carefully assess" airlines' summer schedules.
If the schedules are too ambitious, John Holland- Kaye warned, it might be necessary to ask airlines to cancel more flights.
The schedule changes airlines have submitted in response to the government's requirement to minimize disruption for passengers this summer will be reviewed. Everyone who is travelling through the airport should be confident that their journey will be trouble-free.
After deep pay and job cuts during the Pandemic, airports were unable to hire enough staff to match the recovery. The threat of strike action that would have added to the disruption was averted by British Airways last week.
Despite preparing for the recovery since November, the airport said on Monday that it would not match pre-pandemic staffing levels until the end of July.
There is a blame game going on in the aviation industry. Willie Walsh, the former boss of British Airways who now leads the International Air Transport Association, criticized Heathrow for not preparing for the recovery.
Heathrow should have prepared better according to Walsh. They wanted airlines to operate 80% of their slots through the summer. You would have to be critical of Heathrow because they didn't have enough resources to deal with it.
Philipp Joeinig, the chief executive of Menzies Aviation, which provides check-in services, baggage handling and refuelling for big airlines including benighted easyJet, blamed the government for delays in staff getting security checks, which he said were adding to a mounting crisis.
He wrote in the Times that the government should allow more workers from the EU to ease the shortage of staff. There was a reduction in the available pool of employees.