The carnage continues this morning as photographs show bumper-to-bumper traffic building around the airport.
Weary travellers reported being told their holiday had been scrapped less than an hour before departure.
FlightRadar24 shows aircraft being diverted to a range of airports including those in Germany, France, Ireland and Manchester.
At present 120 planes already circulating Heathrow airspace are being diverted or turned around.
Passengers from across the globe, from San Francisco to Australia have been impacted, with around 1,351 flights to and from Heathrow set to be affected.
This could mean as many as 145,000 travelers see their plans squashed by the closure, according to aviation-data firm Cirium.
Many aircraft have been diverted to Gatwick this morning.
Flights from Singapore, Johannesburg, Lagos, Cape Town and Doha were redirected.
A statement from a London Gatwick spokesperson said: “We are aware of the situation at Heathrow Airport today and we are supporting by accepting diverted flights as required. Flights are operating from London Gatwick as normal today.”
Neil Hansford, head of the Sydney-based Strategic Aviation Solutions consultancy, told The Guardian the fire has triggered a "logistical nightmare".
Surrounding London airports such as Gatwick and Stansted would be unable to manage all of Heathrow's diverted flights.
“These airports can’t take anything close to the volume of Heathrow’s five terminals, where there’s an arrival every minute,” said Hansford.