Early-morning fog disrupted flights at airports on Monday morning.
London City Airport experienced delays while there were 30-minute hold-ups for both incoming and departing flights at Heathrow in west London.
London City said: "Due to low visibility, flights to/from London City Airport are experiencing disruptions. Passengers are advised to contact their airlines for more information regarding their flight status."
A Heathrow spokeswoman said: "We're hoping that the visibility will improve soon."
On the railways, passengers were affected by a series of broken-down train problems.
These caused delays to Greater Anglia services into Liverpool Street station in London as well as hold-ups for First Capital Connect passengers between City Thameslink and Blackfriars stations in London. A broken-down train also led to delays to Northern Rail services between Skipton and Shipley in Yorkshire.
There were also delays and some cancellations to flights at Newcastle Airport due to fog.
On the railways, a signalling problem led to delays to services between Beckenham Junction and Herne Hill in south east London operated by the Southeastern train company.
Another problem with signals led to disruption between Gloucester and Chepstow for customers travelling with the Arriva Trains Wales and CrossCountry companies.
Signal problems also hit services in Scotland, with CrossCountry, East Coast and ScotRail passengers enduring disruption between Burntisland and Aberdour. This meant that replacement bus services were running between Kirkcaldy and Inverkeithing, while some services were diverted or amended.