Virgin Atlantic said the London airport has a "poor track record" of forecasting, having projected 45 million annual passengers for 2022, "when the reality will top 62 million".
"It continues to downplay the strength of returning passenger demand to further its agenda of securing higher charges ahead of the CAA’s final decision," a spokesperson said.
"Airlines have repeatedly warned of the need to use accurate forecasts to inform airport resourcing. By maintaining a deliberately pessimistic outlook, customers risk a poorer airport experience.
"The airport artificially constrained supply in peak summer season to counter a lack of adequate preparation and to win an economic argument that would double passenger charges, despite it being the world’s most expensive airport."
The airline urged Heathrow to avoid passenger capacity limits during the peak Christmas travel window "that would ruin customer plans".
Meanwhile, chief executive of The Advantage Travel Partnership, Julia Lo Bue-Said, described the airport as the "Grinch of Christmas".
"Travellers and businesses are reliant on having a fully functional Heathrow at this peak time, whether they are travelling to see family and loved ones, business travellers or holidaymakers, and the airport should be ensuring that they are planning adequately to meet demand," she added.
"Introducing further caps is not acceptable and not a long-term viable solution every time there is a peak period. The last thing the travel industry needs right now is anything that dampens consumer confidence to travel over Christmas."