Of all SA's weapons acquisitions since 1994, the investment in a new fleet of A400M military aeroplanes announced last week will have the greatest effect so far.

The role of military airlift has been compared with that of the roads built by the Romans to move their legions quickly from one part of the empire to another. Mobility provided by these roads, and the deterrent effect this created, allowed Rome to maintain control over a sizeable empire with a relatively small force.

If SA can turn around its armed forces so as to increase preparedness and be in a position to send far more troops outside the country, this investment in airlift has the potential in the years ahead to substantially increase SA's ability to project power. With by far the greatest military air-transport capacity in sub-Saharan Africa, SA will be able to provide airlift to other countries as well as the planned African standby force. That is significant power in itself a power that will place new demands on SA.

SA needs greater military air transport capacity, and the issues of how many planes it requires and whether it should have decided to buy the A400M are still relevant.

Government says it has still to work out the details, but it will buy between eight and 14 planes for delivery between 2010 and 2014. Investment in 14 A400M transporters will, if the existing fleet of nine C-130s is sold, almost triple SA's airlift capacity, if the air force's Boeing 707 transporters are kept in service

For many defence observers, investment in air transport is the first substantial acquisition that should have been made post-1994 rather than the fighter aircraft, submarines, and corvettes. After all, SA faces no immediate threat.

With controversy still swirling over the arms deal, government may well have been keen to avoid public discussion of another big purchase. Government says eight planes will cost à 837m, about R6,5bn at current exchange rates. Assuming it will get six additional planes at the same price, the purchase will amount to R11,3bn, more than a quarter of the latest price tag on the arms deal.

Because of the sheer cost and lack of consultation, government may be heading into a storm over this decision, particularly as alternatives were never put before the public. The Democratic Alliance has asked why this was not put out to tender and why SA needs the latest generation of air transporters. Government says this is a unique deal and there is no other plane that fits SA's requirements and so it does not require a tender.

Airbus was able to force the timing with its offer. To lure SA into the deal , SA was offered a right to bid on the work over the life of the programme if it agreed to take a minimum of eight planes before the end of this year.

With an ageing fleet of Hercules C130s that must be replaced by 2015, although some were refurbished recently, government would have faced a decision on their replacement soon. There were alternatives to the A400M. It could have bought new or second-hand C-130s, the C-17 from the US, or waited until a Russian programme was more advanced.

The least expensive option would have been additional C-130s, particularly as the US is often prepared to give them away. These cannot take outsize cargo, but to meet its requirements and build in flexibility, SA could have bought more C130s and rented airlift when needed.

One selling point for the C-130 is it has a long, proven record. There is none of the risk inherent in any new aircraft model. Some generals say they would still like to have C-130s as they proved ideal for smaller loads and have a demonstrated performance on rough runways and in hostile environments. The C-17 is best for longer distances and larger cargoes and is beyond SA's requirements.

But the signs are that neither the C130 or C-17 option will be entertained as the government is not keen to rely on US defence technology and has become increasingly close to European contractors.

The A400M transporter is Europe's challenge to US domination of the military air transport. The A400M programme is a joint effort between seven North Atlantic Treaty Organisation countries in Europe in which European defence conglomerate EADS has a majority stake. Delivery of the 180 planes on order, which excludes SA's pending order, is expected to begin in 2009. Of these Germany is taking 60, France 50, Spain 27, the UK 25, Turkey 10, Belgium 7 and Luxembourg 1.

The A400M is positioned between the C-130 and the C-17. It has the advantage of twice the capacity in volume and weight of the C-130. Airbus says the A400M plane can also use rough runways but needs shorter distances for takeoffs and landings than the C-130.

Sales talk from Toulouse is predictably that the plane is ideal for SA's needs as it has the space to carry the outsize cargo the C-130 cannot carry such as the Oryx helicopter. In the A400M, SA has chosen a pricey alternative, one that will meet its goal to have a more air-mobile force. But to make the most of its new transport fleet, big changes will be needed to make the defence force more mobile and efficient.

The argument for SA to buy a new transport fleet has been made all the more compelling by the experience of its peacekeeping operations. In Burundi inadequate road and rail networks, distance and the urgency with which equipment was needed means virtually everything the army needs has to be flown in.

To meet the shortfall in its own transport fleet, SA has rented aircraft from private companies in Ukraine, but the cost of these rentals to fly to hostile areas and the age of these fleets are a growing concern. In extracting troops urgently it is foolhardy to rely on private contractors.

In an emergency, the world's major powers usually come forward either to pay for or provide military airlift for peacekeeping operations in Africa. But it is not clear that this informal arrangement has always worked as it should.

One reason for the hold-up in deploying Nigerian and Rwandan military observers to the Sudan's Darfur region was the delay in airlift, provided eventually by the Netherlands and later the US.

Generals often say no army can have enough airlift. But logistics capacity alone does not keep the peace. It has to be combined with the political will to react with speed to be a credible deterrent

Katzenellenbogen is international affairs editor.

With acknowledgements to Jonathan Katzenellenbogen and the Business Day.