Seizing control of Baghdad's airport could provide coalition forces with a key base to fly in troops, weapons and aid on the doorstep of the Iraqi capital.
Saddam International Airport - renamed by the Americans as Baghdad International Airport - is of major strategic importance.
It is possibly the most significant target in greater Baghdad, outside eliminating Iraqi President Saddam Hussein and his top elite.
Quite apart from strategic concerns, the airport assault will leave Iraqi leaders and Baghdad's citizens in no doubt that the fighting has reached their front door.
Like an island surrounded by outlying fields, the airport is just 20 kilometres (12 miles) to the southwest of Baghdad with an approach road that runs straight to the heart of the capital.
It would be the perfect place for a command centre
Iraqi forces remain in control of this six-lane artery - the Matar Saddam Al-Durwall Road - but it is clear that holding the airport would provide coalition forces with a bridgehead for a full-scale assault on Baghdad.
The airport's main runway, at about 13,000 feet, is long enough to land the military's biggest transport aircraft, as well as civilian jumbo jets.
It also has a second, 8,000-foot landing strip, once used by Iraqi fighter jets, which would be useful in the provision of essential supplies.
Holding the vast airport complex - several miles in diameter - would allow the Americans to leapfrog their supply-chain up from Kuwait.
Colonel John Peabody, of the Third Infantry which advanced on the airport, said: "We are a military power working to achieve a political goal - the overthrow of a regime. Taking the airport makes a dramatic political statement, but it's also strategic."
'A perfect base'
The airport site is likely to be earmarked as the coalition's headquarters, according to military experts.
Major Charles Heyman, editor of Jane's World Armies, told BBC News Online: "It would be the perfect place for a command centre.
"The communications are good - airport communications always are. It is the perfect distance from the city centre. It doesn't look as if there will be a great missile threat to incoming aircraft."
UN sanctions halted civilian air traffic to the airport
One of the first priorities for US troops will be to secure the area around the airport, and to protect incoming and outgoing flight paths for aeroplanes and helicopters.
A mile or so to the north east of the airport perimeter is the Presidential Palace North. To the east are the Abu Ghurayb presidential grounds and to the south west, the Radwanlyah Palace complex.
'Smoked glass and mirrors'
US Central Command says that troops discovered "underground facilities" beneath the airport, and there are reports of a section of tunnel stretching back to the Tigris river.
Dr Toby Dodge, an Iraq expert from the UK's University of Warwick, said he would not be surprised if there was "some form of bunker complex" beneath the airport, which was built in 1985.
The airport is a key strategic and political target
"This is a very 1980s building. It is all smoked glass and mirrors in the terminal, and it dates from a time when Iraq's top brass would have been flying out of the country on a regular basis.
"It would not be surprising if they had some form of protected complex where they could wait before boarding their flights," Dr Dodge told BBC News Online.
Civilian air traffic at the airport ceased when international sanctions were imposed on Iraq days after President Saddam Hussein sent his forces into Kuwait in August 1990.
But the isolation ended in 2000 with the arrival of flights from dozens of non-governmental organisations and countries seeking an end to the UN sanctions.
The Iraqis were reported to have dispersed nearly 40 passenger airliners to foreign airports before the first Gulf War, to protect them against possible bombing. Iraq has had trouble retrieving them.
The sanctions made Baghdad among the few capitals in the world inaccessible by scheduled international flights.