Passengers are facing further disruptions as Heathrow Airport cancelled 100 flights on Saturday.
Heathrow Airport has cut the number of flights on Sunday by 20%, after 2-6cm of snow was forecast.
The airport said 67 of those flights were departing and 33 arriving. But both runways remain open and the airport is returning to normal.
Details of which flights will be cancelled will be announced by airlines when they have finalised their schedules, the airport said.
Heathrow has already cancelled 100 flights on Saturday - 67 departing and 33 arriving.
Since Saturday morning hundreds of people have queued at BA's check-in desks at Heathrow's Terminal 5
But both runways remain open and the airport is currently said to be returning to normal.
On Friday more than 400 flights were axed and thousands of passengers ended up sleeping in the airport.
On Friday more than 400 flights were axed and thousands of passengers ended up sleeping in the airport.
British Airways (BA) apologised to people who were stuck on planes as snow delayed and cancelled their flights.
Some are angry, some are laughing it off, but most look tired and frustrated.
Some passengers were kept waiting on board aircraft for hours to use take-off slots as soon as they became available, while others complained they were unable to collect their luggage.
Each passenger has their own story, a birthday trip to Paris cut short, a skiing holiday hanging in the balance, a long flight home delayed indefinitely.
'Refugee camp'
"You get two inches of snow? We get two feet" says a man from up state New York, adding that the disruption it causes here makes him "giggle".
BA said it was "doing all it could" and said customers could rebook their flights if they did not want to travel on Saturday or Sunday.
For some it is a second frustrating day in the terminal. Sleep is not easy under fluorescent lights on a hard concrete floor. Airport staff seem to be eager to help, but they cannot bring much good news to those who just want to know when they can fly.
Simon Calder, travel editor of the Independent, said Terminal Five no longer looked like a "refugee camp", which it had overnight.
Although the congestion has eased, there is a warning more snow will cause more delays.
Despite the fresh cancellations, mostly for short-haul flights, on Saturday the west London airport said about 44 aircrafts were taking off and landing every hour.
But there were disruptions as it was trying to clear the backlog from Friday.
Passengers arriving at the terminal are being advised not to join the queues unless their flight is within two hours, in order to manage the congestion.
A Heathrow spokesperson said: "Both runways, and all stands and taxiways are open at Heathrow this morning with no restrictions.
A Heathrow spokesman said: "Latest forecasts for tomorrow show a high probability of around 2-6cm of accumulating snow and low visibility at periods throughout the day.
"We do not expect significant snowfall today, but temperatures are forecast to remain around zero degrees or below and there is the possibility of low-visibility conditions".
"This will reduce the capacity of the airport and without action would cause significant disruption to passengers and flights."
But the airport warned that passengers could face problems on Sunday.
He added that in low visibility more space needs to be left between aircrafts, which was difficult at Heathrow as it runs at almost full capacity.
"There is a chance of further snow tomorrow, with a potential accumulation of between 2cm and 5cm from 11:00 GMT and we will be talking to airlines today about tomorrow's schedule".
He added there was "simply no room to reschedule the delayed flights."
'Mildly hysterical'
In other developments:
On Friday, the freezing conditions forced the closure of a runway for de-icing, as the airport's usual number of 42 take-off and landing slots an hour was reduced to six at one point - and an average of 26 for most of the day.
Despite Saturday's cancellations, mostly for short-haul flights, the west London airport said about 44 aircrafts were taking off and landing every hour
BA apologised to people who were stuck on planes on Friday, as snow delayed and cancelled their flights, and said customers could re-book their flights if they did not want to travel on Saturday or Sunday 'Mildly hysterical'
Priority for the slots was given to long haul flights whereas most BA services are short-haul, a spokesman said.
On Friday, passenger Ian Aitchison, who was due to the US for a conference, said he was on a plane for more than six hours before the flight was cancelled and he was then told he would be unable to get his luggage back and has to arrange to have it sent later.
A spokesman for British Airways said: "There will be knock-on disruption to services on Saturday and we are advising all customers to check the very latest status of their flight via ba.com before leaving for the airport and if their flight has been cancelled not to leave home."
"It's pretty funny. To be honest I'm mildly hysterical... obviously there's a lot of people who are quite upset."
Passenger Ian Aitchison, who was due to fly on Friday to the US for a conference, said he was "mildly hysterical" about being on a plane for more than six hours before the flight was cancelled and he was then told he would be unable to get his luggage back.
Jamie Methuen was supposed to fly to Geneva on Friday and then travel to France for a skiing weekend.
"We're trying to get our luggage back, of course, and BA have told us we can't have our luggage so all the suitcases are being held of all the people who are on the cancelled BA flights.
He told the BBC his flight was cancelled after a four-hour wait at Heathrow, and that he would have "appreciated a far more honest and pragmatic approach" from the airlines, "four hours earlier".
"So, I'm with a party of people here flying over to the US, and we're all trying to find ourselves hotels. We've not got our cases.
"It will be sent on alternative flights or you can arrange to have it sent to you through the website.
"It's pretty funny. To be honest I'm mildly hysterical... obviously there's a lot of people who are quite upset.
"Mostly people are just confused and dazed rather than shouting and swearing."
'It's miserable'
He said airline staff had been very "polite and helpful" walking around talking to passengers but "the problem is that they don't know what's going happen next".
Jerry Meng, from Los Angeles, spent Friday night at the airport after his 11:00 GMT flight to New York was cancelled.
He said: "There are lots of bodies lying around in the airport. If feels like there's been a natural disaster.
"The staff have been helpful, they've been handing out blankets and water bottles.
"It's miserable - but that's nature. It's better to be safe and protect peoples' lives."
British Airways has offered refunds and overnight accommodation to customers, or letters for customers to make a claim at a later date.
On the trains there are delays of about half-an-hour between the UK and France.
There are also delays of between 40 minutes and 50 minutes on the First Capital Connect and Southern trains.
On London Midland there are delays of up to 30 minutes and passengers have been warned of cancellations at short notice.
