At 9pm on Sunday night, around 300 passengers waiting at Heathrow for British Airways flight 245 to Buenos Aires discovered they would be not be waking up in an Argentinian midsummer. Instead, they faced the prospect of having to sort out their own hotel rooms many miles away, or sleeping on the floor of Terminal 5.

Like 50,000 other BA passengers, they will start Monday far from where they planned to be, after the airline's operation juddered almost to a halt at Heathrow. More than 140 outbound short-haul flights, and 26 long-haul departures, were cancelled on Sunday. BA has cancelled a further 70 short-haul round trips on Monday, plus nine long-haul flights including departures to Rio, Tokyo and Los Angeles. An additional 15,000 people will be affected by these latest cancellations.

Departures from Europe’s busiest airport began to go wrong before dawn on Sunday. Torrential overnight rain meant that de-icing could not begin until the first wave of planes were ready to go. Delays quickly built up: the 7am to Geneva left four hours late. And as queues developed while sleet and snow fell, aircraft that had already been de-iced needed to be treated again as ice began to build up on their wings while they waited for clearance to depart.

BA operate an ambitious schedule, which most of the time works remarkably well. But not on Sunday. At 10am, a sweep of around 20 proactive cancellations was made by British Airways operations staff, to create “firebreaks” in the schedule in a bid to avoid further cancellations. Within an hour, that number had doubled. And quickly the first seriously wintry day at Heathrow became a bonfire of the schedules.

Other airlines were mildly affected, with Austrian Airlines, KLM, Lufthansa and Swiss cancelling flights to and from their hubs, but for BA — which has a majority of the slots at Heathrow — the unravelling was of an entirely different order of magnitude.

Initially passengers on long-haul flights waiting to leave Terminal 5, or at European airports heading for Heathrow, faced irritating delays exacerbated by hunger. From Athens, Frank Durrell tweeted: “Come on @British_Airways. 1 hour delayed boarding. 1.5 hours stuck in this plane waiting to leave. And now told we will be 4 hours late landing. Would have just gone back to hotel if I’d known at the start.

“And now no snacks available at all. No complimentary food, must buy M&S food and it ‘can’t be given away’. Pilot tried to get more snacks locally and couldn’t. Pilot wants to get us ‘vouchers on arrival’ but doesn’t think he can. Terrible service.”

Gradually, the scale of the problem became clear. With aircraft blocking stands, British Airways planes that did make it to Heathrow had to wait sometimes for hours to be unloaded. When space on the ground ran out, the diversions began.

Passengers from Newcastle got no further than Leeds-Bradford, where they were joined by confused travellers from Kiev and Warsaw. Back on Tyneside, Newcastle airport welcomed divertees from Paris, Reykjavik, Helsinki, Frankfurt and Athens; Frank Durrell tweeted once more: “You suck. Diverted us to Newcastle. Why didn’t you just let us stay in Athens and fly us back tomorrow?”

Passengers from Zurich, Zagreb, Vienna, Gibraltar, Nice and Madrid are mingling in Cardiff. Milan, Prague and Berlin passengers had an unexpected visit to Bournemouth, while along the road BA travellers from Geneva and Krakow congregated in Southampton. The late-night passengers from Istanbul flew around in circles over the Home Counties for a while, hopeful of landing, before diverting to Liverpool.

BA film plane landing from cockpit in Johannesburg

Long-haul inbound flights from Dubai, Mumbai and New York landed at Paris, Frankfurt and Dublin respectively. At times of disruption British Airways does everything it can to protect the long-haul schedule. Slots for smaller planes flying shorter distances are sacrificed to enable big aircraft to take large numbers of people across oceans. But at Heathrow on Sunday, even that principle had to be abandoned.

One by one, crews went “out of hours,” when it became no longer possible for them to fly the mission within legal limits. Three New York services were cancelled as well as two each to Dubai and Toronto, with many Asian flights also grounded including the key departures to Hong Kong and Singapore.

For each cancelled outbound departure, there is an equal number of inbound flights that have been grounded. While the passengers in Buenos Aires and other far-flung locations have plenty of warning of the cancellation, those closer to home do not enjoy the luxury of time or, often, information.

Sarah Griffiths tweeted: “Parents stuck in Pisa airport for 6hrs and British_Airways has made 1 announcement & ignored all consumer rights. Rep’s done a runner?! They’re tired & freezing. Rubbish.”

The Independent has calculated 27,000 BA passengers are stranded in London, a further 20,000 stuck in European airports, and another 3,000 at airports elsewhere in the UK and neighbouring countries after their flights to Heathrow were diverted.

With so many planes and crews out of position, even if Monday’s conditions at Heathrow were perfect, it would take several days to get everyone where they needed to be. But sub-zero temperatures are forecast for the airport, and the flow rate is to be reduced — hampering BA’s efforts to get back on schedule and possibly leaving even more passengers out of position.

The airline is offering passengers booked to fly on Monday the option to re-book on alternative flights up to Monday December 18, free of charge.

Heavy snowfall across Britain: in pictures Show all 18 1 /18 Heavy snowfall across Britain: in pictures Heavy snowfall across Britain: in pictures A snowplough clears a closed road on the A470 from Merthyr Tydfil to Brecon PA Heavy snowfall across Britain: in pictures Pedestrians walk over the Millennium Bridge with St Paul's Cathedral pictured in the background as snow falls AFP/Getty Images Heavy snowfall across Britain: in pictures Snow in Wood Green Rex Features Heavy snowfall across Britain: in pictures People walk through the snow in a park in north London EPA Heavy snowfall across Britain: in pictures Two girls make a snowman on Primrose Hill PA Heavy snowfall across Britain: in pictures People wake up to a blanket of overnight snowfall in Stoke On Trent Getty Images Heavy snowfall across Britain: in pictures Harlequins win a line-out in heavy snow during the European Rugby Champions Cup match against Ulster Rugby at Twickenham Stoop Getty Images for Harlequins Heavy snowfall across Britain: in pictures A train travels along snow covered tracks in High Wycombe EPA Heavy snowfall across Britain: in pictures Families take to the hills with sledges near Edale in Derbyshire AFP/Getty Images Heavy snowfall across Britain: in pictures People push a car up a snowy hill in north London EPA Heavy snowfall across Britain: in pictures A crashed lorry on the A50 is tended to by police as the snow falls near Uttoxeter REUTERS Heavy snowfall across Britain: in pictures People go sledding on Primrose Hill PA Heavy snowfall across Britain: in pictures Motorists brave the snow in Worcester PA Heavy snowfall across Britain: in pictures An abandoned car on the roadside on the Snake Pass in the Peak District PA Heavy snowfall across Britain: in pictures Heavy snow falls on sheep in the hills near Sennybridge, Wales REUTERS Heavy snowfall across Britain: in pictures Snow falling on Westminster Bridge Rex Features Heavy snowfall across Britain: in pictures Walkers on The Long Walk at Windsor PA Heavy snowfall across Britain: in pictures Motorist braves snowy conditions on the M2 motorway near Gillingham PA

British Airways is telling passengers: “Heathrow has experienced unpredicted severe adverse weather conditions and that is expected to continue into Monday.

“Temperatures have remained low, and safety is our number one priority, there is a requirement to de-ice every individual aircraft before it departs. We are sorry for the difficulties caused by the poor weather and will do all we can to minimise the effect it has on our operations.

“We apologise for the inconvenience, and we would like to assure customers that we are doing everything we can to get as many people away on their flights as possible.

“As a result of the forecast we have agreed with Heathrow Airport, National Air Traffic Services (NATS) and other airlines to reduce our flight schedule from Heathrow on Monday December 11.

“Please do not travel to the airport if your flight has been cancelled.”

A Heathrow spokesperson said: “Heathrow airport remains open however we regret that weather across the UK is resulting in some passengers experiencing disruption to their travel arrangements. Airlines are responsible for ensuring their flights are fully de-iced before they are operated and this is resulting in some delays and cancellations.”

Why do planes need to be de-iced?

A build-up of ice on an aircraft wings adds weight, increases drag and, crucially, changes their shape in a way that significantly reduces lift. It is thought to have been a factor in the 2009 crash of a Colgan Air flight from New York to Buffalo in which 49 people died; shortly before they lost control, the crew discussed a build-up of ice. In flight, it is dealt with by heating the critical surfaces, notably the leading edge of the wings. But before take-off any build up of ice must be removed from the outside, by spraying on a hot mix of propylene glycol and water. The procedure is time-limited, and in extreme conditions while de-icers work on one side of a plane the ice builds up on the other, just cleaned side.