Source: Sharecast
The privately financed project, worth £2.2bn, will see the current northern runway move 12 metres so that it can be used simultaneously as the main runway.
Currently, the northern runway is only used as an emergency runway for taxiing aircraft, or as a backup when the main runway is closed, as it it too close to the main runway.
The government said the project was a "no-brainer" for the economy, which will add 14,000 jobs and generate £1bn a year.
The plans have been in place since February, though the airport has since agreed to noise mitigation and enhanced public transportation measures following concerns from local communities and planning inspectors.
Gatwick, which currently runs 280,000 flights each year, is expected to handle up to 390,000 by the late-2030s under the current plans.
“The transport secretary has cleared Gatwick expansion for take-off. With capacity constraints holding back business, trade and tourism, this is a no-brainer for growth," a government source said.
“This government has taken unprecedented steps to get this done, navigating a needlessly complex planning system, which our reforms will simplify in future."