Transport Secretary Heidi Alexander is set to approve plans to bring Gatwick's emergency runway into routine use, ahead of Thursday's deadline for her decision.
The Cabinet minister told aviation leaders that the planning application is "literally on my desk".
She dismissed suggestions she would block airport expansion on environmental grounds.
"I am not some sort of flight-shaming eco-warrior. I love flying. I always have," Alexander declared at the annual dinner of trade body Airlines UK. The Government believes in "increasing airport capacity", she added.
Heidi Alexander dismissed reports she is an 'eco warrior'
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Members of CAGNE (Communities Against Gatwick Noise Emissions) stand near the perimeter fence at London Gatwick Airport
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The £2.2billion privately financed project would enable the West Sussex airport to handle 100,000 more flights annually. It involves moving the emergency runway 12 metres north and bringing it into regular operation.
The plan includes extending both terminals, installing new aircraft gates and remodelling taxiways. Road connections to both terminals would be enhanced with flyovers to separate local traffic from airport vehicles.
Passenger capacity would increase from 45 million to 75 million annually, with the upgraded runway operational by the end of the decade.
The Civil Aviation Authority (CAA) has expressed support for Gatwick's expansion, saying it would bring "benefits to consumers" even with Heathrow's potential third runway.
LATEST ON THE HEATHROW EXPANSION PLANS
Activists from Fossil Free London and Green New Deal Rising take part in a protest against a third runway at Heathrow, and expansion at Gatwick
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Gatwick is the UK's second busiest airport
PAThe aviation regulator noted that "Gatwick's airline and passenger base is significantly different from that using Heathrow".
Benefits would include "meeting the demands of passengers in the choice of destinations, enhanced competitive pressure on airlines and greater resilience of airport infrastructure".
The CAA published its final proposals yesterday to accept Gatwick's commitments for the next four years, including a price cap limiting charges to airlines.
Alexander told aviation leaders that the government must balance economic growth with environmental protection.
"Some might say the current national debate about airport expansion highlights a fundamental tension between growing the economy, whilst protecting the environment. I say we must do both," she stated.
Secretary of State for Transport Heidi Alexander claimed she loved flying
PAShe acknowledged "capacity problems, particularly at airports in the South East".
Her role as "decision maker" requires striking a balance between potential benefits and "tough questions" about climate obligations, noise minimisation and fair cost distribution.
The government will do "all we can to support the sector and take the brakes off growth," she added.
The airport says its scheme is "shovel ready" and construction could start this year if approved. Gatwick expects the project to create £1bn per year in economic benefits and generate an additional 14,000 jobs.
Operating as a two-runway airport would enable Gatwick to add around 10-15 flights per hour at peak periods. The total annual number of flights would rise from 280,000 to 380,000.
Local campaigners have expressed concerns over impacts on surface transport, noise, housing provision and wastewater treatment.
