We're spending $17 billion on 72 F-35 fighters, or $240 million for each. A cruise missile costing $1-2 million can easily destroy several, flying over their airbase and dropping small explosive charges like confetti.

It gets worse. After a multi-missile attack, hundreds of the bomblets may be left lying around the airfield, unexploded, and must be removed before aircraft can safely move.

Surviving aircraft may be unable to go anywhere, anyway, because other missiles, maybe big ballistic ones costing $20 million, could have slammed into runways and taxiways, blasting craters in them, throwing around debris and leaving the surfaces unusable.

Aircraft are trapped until the mess is cleaned up and the surfaces repaired.

So they sit there, waiting for the next attack.

None of this is a new problem, and there are several old solutions - or partial solutions - most involving pouring a lot of concrete. It's a disgrace to the Department of Defence that we have barely done any of this, while as late as 2022 we were still ordering vastly less important things, such as armoured fighting vehicles.

A think tank in Washington, the Center for Strategic and International Studies, has just issued a report on what would happen in the Western Pacific if China started a war to seize Taiwan.

The researchers got their results by designing a war game - using a map and counters that represented the forces on each side - and playing it 24 times. Such simulations, often done with software instead, are well established ways of seeing what weapons and strategies are worthwhile.

One particular result should have gripped the attention of our air force: about 90 per cent of US, Japanese and Taiwanese aircraft lost in the simulations were not shot down; they were smashed on the ground.

They were destroyed in their hundreds, left as smoking wrecks that bulldozers shoved aside as (imaginary) base personnel struggled to get the facility back into operation.

The six northern air bases, from Exmouth to Townsville, that we would use in such a war face a risk that is in some ways less and in some ways worse.

It's less because Australia is farther from China, so missiles needed to hit our bases would, on average, be bigger and more costly than those thrown at Taiwan, Japan or even islands out in the Pacific used by US forces. If weapons cost more, probably fewer will be available.

Also, in any such war, most of those distant Australian airbases would be well down China's priority target list.

But we've made our risk worse by leaving our bases almost completely unprepared for such attacks.

Anyone thinking about this will quickly wonder whether aircraft should be kept in tough concrete buildings for protection. And in fact that is just what is needed.

Such buildings are called hardened aircraft shelters.

We don't have any.

Instead we have weather shelters - basically, carports - that are about as protective as they sound.

It will be astounding if the review of defence policy due to report in the next few weeks does not tell the government to rapidly toughen up our northern airbases with hard shelters and many other measures.

None can be a perfect solution. But the idea is to drive up the cost of attacks on a base, so they would be less intense and less frequent, and to prepare each airfield to quickly recover from damage and get back into action.

For example, a big missile might still bust into a concrete shelter and destroy the aircraft inside. But that means it can't be a small, cheap missile, and it would destroy only one aircraft, not several.

Its success would depend on the thickness and strength of the concrete and on cunning structural features that can cause a missile's penetrator to malfunction.

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Such shelters for fighters can cost only about $10 million each, though they get pricier as they get tougher. For bigger aircraft, the price would be much higher.

That still leaves us with vulnerable runways and taxiways. The answer there is to have more of them and make them longer, so more missile hits are needed to halt operations. So: more concrete.

Also, the base needs to have plenty of construction equipment, materials and trained people to fix surfaces as quickly as possible. The air force does not seem to have paid much attention to that.

The bases must provide strong protection for fuel, weapons, maintenance facilities and, above all, people.

That's yet more concrete.

Another answer is to have more bases, spreading aircraft around, lessening the risk of losing too many at once and improving the chance of maintaining airpower from at least one airfield while others repair their damage.

We can also use concrete that we already have: civilian airfields in northern Australia and maybe its plentiful stretches of straight road.

For those, we need teams of people and equipment that can rush to such places and turn them into temporary bases, then pack up and move on to another before an attack arrives.

Such temporary bases could indeed be used to recover aircraft that could not return to a permanent base because it had been wrecked while they were in flight.

Buying defence systems that shoot down incoming missiles should be another measure, though they would be expensive.

Our northern airbases are soft targets designed in the days when our main military worry was the unlikely one of war with Indonesia. Those days are over. It's time to toughen up.