BA said ticket sale suspensions were being dealt with on a case-by-case basis, with no blanket restrictions being imposed.
For example, if ticket sales for a morning flight to New York were paused, travellers may still be able to book themselves on to an afternoon flight.
Heathrow announced last month that a cap of 100,000 people per day would be allowed to fly until September 11.
It comes after short-haul flights to Europe were suspended by BA until August 8.
BA also announced it would cancel 10,300 flights until October, with one million passengers affected.
The airline is now limiting the number of seats it is selling on each flight to ensure it stays under the limit.
Fares are still available to book on BA flights arriving into Heathrow.
In a statement to the Standard, the airline said: “We took pre-emptive action to reduce our schedule this summer to give customers certainty about their travel plans and to build more resilience into our operation given the ongoing challenges facing the entire aviation industry.
“When Heathrow introduced its passenger cap, we took a small number of additional flights from our schedule and to continue to comply with the cap.
“We’ve been taking responsible action by limiting sales or all the available fares on some of our Heathrow services to ensure more seats are available to rebook customers.
“We’ll continue to manage bookings to be within the Heathrow imposed cap so we can get our customers away as planned this summer.”
The airline has been criticised over the decision amid concerns it could push up prices for flights with other carriers.
Over summer months many passengers flying to and from the UK’s busiest airport have suffered severe disruption, with long security queues and baggage system breakdowns.
Tens of thousands of flights have been cancelled across airlines to cope with the demand for air travel amid staffing shortages.