Migs would only have carried a limited threat

Any rented fighter jets will be a significant boost to Ukraine, particularly as Russia has so far failed to achieve air superiority. But even if Ukraine manages to take delivery of the 28 MIG-29 fighters offered by Poland this week, it will take time for the jets to be as effective as they need them to be in the skies over their country.

Designed originally to race into the air to take on American F-15 and F-16 combat aircraft, the jets have been developed over the years to be able to strike ground targets, including with precision guided munitions. In the hands of Ukrainian pilots they would be a “thorn in the side” of Russian air and ground forces, a defence source said, but they are limited.

The Russian-made aircraft are strong, sturdy, reliable, competent and can turn on a sixpence, but with big engines and small fuel tanks they have very little endurance. They are not built to the same standards as western aircraft; the tolerances are much lower. As such they are quite a bit heavier than a US F-16 or RAF Typhoon, and whilst they may be able to carry state-of-the-art weapons, the airframes are less modern.

Further, there are questions about where all the additional spare parts would come from to keep the fleet operational. Without additional spares, at least half of the Polish machines would quickly turn into glorified Christmas trees, supplying spares for the rest of the fleet.

Even with an established support system, a maximum of about 10 aircraft from this extra tranche would be expected to be serviceable and ready to fight on any given day.

However, there is much more to employing air power than simply having airframes available.

Pilots, mechanics, avionics technicians and airspace managers are just some of the roles needed to deliver military power from the skies. All of them must be available on the day. And where would they fly from? Ukraine has limited options. Russia failed to land many cruise missiles on the country’s military runways at the start of this campaign, but holding the fleet all in one place invites disaster.

Equally, splitting the fleet up in a bid to protect the jets would create operational headaches when the order to launch missions was sent.

It is possible Ukraine could set up a temporary forward operating base on a motorway in the west of the country, under the protection of an air defence umbrella. The RAF practised for these sorts of scenarios during the Cold War, but they’re not easy, and it is unlikely any air force could set up such a contingency with no notice.

The issue of gifting the Migs to Ukraine has raised other issues.

The plan to send the aircraft, possibly via the US Air Base in Ramstein, Germany, has seemingly crossed a red line.

Western politicians and Nato officials were left scratching their heads this morning, wondering where the threshold of acceptable and unacceptable lethal aid lies.

Could Ukrainian pilots fly the jets from Poland? Was Poland seeking to spread the risk by announcing – seemingly without negotiating first with Washington – they would send the planes to Ramstein?

Would Vladimir Putin – a man known to like taking risks and who has repeatedly raised the spectre of nuclear weapons – deem the supply of Soviet-era fighters from the West a step too far?

Britain’s Defence Secretary was blunt in his analysis. There would be “blowback for Poland if it happened”, Ben Wallace said.

However, Eduard Heger, prime minister of Slovakia, a Nato member, seemed to disagree. “We are all united in this, the risk is always ours together as Nato, the EU or Europe,” he told Radio 4’s Today programme. “It’s not about individual countries, because Ukraine is fighting for democracy.”

Western officials think Mr Putin would use nuclear weapons if his regime was threatened, and then only – initially at least – as a demonstration: a “small” battlefield nuclear strike against an airfield, or a detonation in the atmosphere above a city to knock out power through the electromagnetic pulse.

Poland was unwise to force the US to decide whether it thinks Mr Putin would view sending the Migs from Ramstein as sufficiently escalatory to threaten the use of nuclear weapons.

An unhelpful precedent has been set regarding the threshold of what lethal aid is acceptable and what is not.

Mr Putin will now do all he can to push that threshold down in order to stop the flow of tank-busting missiles wrecking his military ambitions.

In the meantime, the Mig-29s are still in Poland and Ukraine is still being pounded from the air.