London is a major airport system. There are 4 busy airports: Heathrow Airport in the west, Gatwick Airport in the south, Stansted Airport and Luton Airport in the north. Generally, you may need to transfer between these airports. The distance between them is relatively long, it is best to arrange transportation in advance.
Between these two busy airports. Thanks to the well-developed transportation network, traveling from Gatwick Airport to Heathrow Airport is very easy. It takes about 50-60 minutes to pass M25. However, this route is usually heavily congested during morning rush hours (from 6:30 to 10:00). If you plan to travel during this time, please consider leaving 15 to 30 minutes in advance. There are also coach and train options. The National Express provides a 25-minute direct ride at a fare of £25, while there is no direct train between Heathrow Airport and Gatwick Airport. You may need to take 2-3 trains, which is time-consuming and inconvenient.
London Stansted Airport is 48 kilometers away from central London and 69 kilometers away from Heathrow Airport. It is the base of several major European low-cost airlines (Ryanair, easyJet, Jet2.com). Stansted Airport currently serves more than 170 destinations, more than any other airport in the UK. From Stansted to Heathrow Airport, it is a common means of transportation for travelers. It takes about an hour to take the M25 car. On this route, it is recommended to take a taxi, because your transit time will not waste time, and this will affect your flight schedule.
The fourth airport serving the London metropolitan area is London Luton Airport, 46 kilometers from central London and 55 kilometers from Heathrow Airport. The fastest solution is a London taxi, which may take 40 minutes under normal traffic conditions. You can relax, because the route between Heathrow and Luton Airport is not as busy as Gatwick Airport.