Thousands were stuck overnight and few flights will depart on Sunday. Hundreds more slept at Gatwick, as knock-on delays hit most UK airports, according to the BBC.
The Met Office warns of more heavy snow in Yorkshire, north-east England and eastern Scotland, advising essential travel only in the Edinburgh area, it added.
Icy roads affect much of the rest of the UK. There is some rail disruption.
It pointed out that an extreme weather warning is in place for Edinburgh, Lothian and Borders, with some 15 to 20cm (6-8in) of snow expected between 1100 and 1800 GMT.
Up to 10cm (4in) are expected in other snow-affected areas, with up to 20cm on high ground.
Temperatures struggled to get above -5C (23F) overnight and BBC forecaster Matt Taylor said there were lows of -19C (-2F) in parts of Worcestershire and Shropshire. They are likely to stay below freezing throughout the day.
The Met Office also issued warnings of heavy snow in parts of the north-east of England, Yorkshire and Humber, Sussex, East Sussex and Kent on Sunday.