A spokesperson for British Airways said: "When [we] are not able to operate flights into Heathrow as planned, we do our best to keep customers updated, and look after them, providing refreshments and hotel accommodation."
Reduced capacity at Heathrow as heavy snow fell on Sunday meant a number of British Airways flights were forced to divert to airports including Leeds and Newcastle, while other aircraft were held in holding patterns above the UK waiting for a window to land.
"We are working with Heathrow and Air Traffic Control to operate as many of our flights as possible into the airport. Safety is always our priority, especially when dealing with very challenging weather conditions," the spokesperson added.
"We understand this is a frustrating time, but our teams are working around the clock to ensure we get customers to their destinations quickly, but safely."
Other airlines using Heathrow also had flights impacted.
The airport said the disruption would continue on Monday "due to crew and aircraft being out of position".
"Before coming to the airport, passengers must check their flight status with their airline," the airport said.
"If the status of your flight is cancelled, please do not travel to the airport."
Flights at other London airports were also affected on Sunday, while services were suspended from Birmingham and Manchester, too. Ryanair and EasyJet advised customers to check their flight status before travelling to the airport.
The European Organisation for the Safety of Air Navigation said disruption would continue across Europe today. Nice, Brussels and Amsterdam were all suffering from delays.