Air and rail passengers are being hit by more disruption after record-breaking temperatures caused travel chaos on Thursday.
Flights from London airports, including Heathrow and Gatwick, have been delayed and cancelled due to the weather.
Disruption is also being caused by a technical problem with the UK’s air traffic control system.
Train services have also been delayed and cancelled after the second hottest day in the UK was recorded on Thursday.
Rail companies feared rail lines would buckle – but it was sagging overhead cables that led to problems.
Martin White and his wife were stuck at Naples Airport after their Thursday night flight to Gatwick Airport was cancelled due to the weather.
“Everybody is packed liked sardines and there are fraying tempers,” Mr White said.
Friday has been cooler than Thursday, with temperatures ranging from 23C to 25C in most areas (73F to 77F), rising to 27C in south-east England.
During the day it is expected to be mostly dry but rain is expected to develop across northern and eastern areas of the UK overnight.