CIA director William Burns said last month that Chinese President Xi Jinping had ordered his military to be ready to seize Taiwan by 2027. That doesn't mean war is scheduled for 2027, but it does mean that as soon as four years from now the danger will be high.

For our own sake, we will almost certainly need to help the US in any war to defend Taiwan.

But it is already too late to do much to prepare for a war in 2027 - above all because the Coalition government kept following directions from our irresponsible defence establishment, ordering irrelevant equipment according to plans that the rising China threat had made obsolete.

Then Labor missed chances to get things moving as soon as it took office last year.

This column spent this week at the Australian International Airshow at Avalon, Geelong, speaking to people in the defence and aerospace industry to gauge how quickly we could expand the air force. Nothing we can do with the navy would be quick, except buying more ammunition for it. And the army is just about useless, though it may gain a relevant strike-missile function late in the decade.

Luckily, we have heavily modernised the air force over the past 15 years, so almost all the important types it has in service are still coming out of warm production lines overseas. We already know how to operate those types. So we can quickly scale up.

But not much by 2027.

If we placed an order now, we could begin receiving Airbus A330 MRTT tankers next year to add to the seven that we already have (and call KC-30As). Tankers make other aircraft more useful. For example, they can enable fighters to attack more distant targets or to stay on patrol for longer.

We can get more tankers so soon because, Airbus tells me it needs only 18 months to convert second-hand A330 airliners into MRTTs. Lots of A330s are lying around idle as the airline industry struggles to recover from the pandemic.

It would be no mistake to expand the tanker fleet to 20, since the number of aircraft that will need refuelling will also expand. Also, in a war over Taiwan our planes would have to fly very long distances.

Lockheed Martin says it could begin delivering more F-35s within four years of an order placed in 2023 (though we notice that its manufacturing program is behind schedule).

That would not mean we could get a complete batch of, say, 30 more F-35s in 2027; they'd probably arrive over the course of two or three years.

Also around 2027 we could begin receiving more P-8A Poseidons - anti-submarine, anti-ship and surveillance aircraft that would be in high demand in a Western Pacific war. The manufacturer, Boeing, declined to discuss timing for any of its models, but recent Poseidon orders have generally been followed by deliveries four years later.

In 2028, or maybe 2027, we could expect to receive more precious Boeing Wedgetail aircraft if we ordered now. Wedgetails have powerful radars that produce a picture of what's going on for hundreds of kilometres around them. Like tankers, they multiply the value of other aircraft.

They're built by adding equipment to the business jet version of the 737 airliner. Boeing appears to be unable to step up production of that variant, but we can get second-hand planes for conversion. In fact, the RAAF already has two 737 business jets. They're pretty old but may be good enough.

We would never regret buying four more Wedgetails.

Two other types should enter Australian service this year, the MC-55A Peregrine radio-intelligence collector and the MQ-4C Triton maritime patrol drone. I guess additional orders would result in deliveries beginning in 2026 or 2027.

The government needs to think quickly about another order for the EA-18G Growler, an electromagnetic attack version of the Super Hornet strike fighter. We currently have 12 - one for every eight fighters.

If we want to maintain that ratio as we expand the fighter fleet, we must order more Growlers now, because Boeing says it will shut the Super Hornet production line as soon as 2025.

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That raises the possibility that we could get more Growlers in 2025 or 2026 - if indeed Boeing is interested in supplying them. (There's reason to think it needs to switch resources to building a secret new fighter for the US.)

That also means we could start receiving more Super Hornets at about the same time. The RAAF would surely prefer more F-35s, but Super Hornets are good aircraft and the government needs to consider the value of speedily expanding the air force's strike wing, which uses the type.

A new and surprising possibility emerged at the air show. Boeing said it hoped that Australia would order F-15EX fighters. The F-15EX is a modern version of a very old design, and the US is buying it. Valuably, it has greater range than the Super Hornet.

How quickly we could get F-15s isn't clear, but 2025 may be realistic. Adding a third fighter model to the air force would not be ideal, but the bigger problem in these stressful times is that making a new type operational would probably take two more years - so we'd again be talking about expanding capability not before 2027.

There's an old joke about asking for directions to Dublin and getting the answer "I wouldn't start from here."

Well, here is where we are. We're in 2023 and have done almost nothing to expand our forces in the second half of the decade.

We have left things too late.