Jets to Ukraine: Crucial questions over supplying F-16s to Kyiv
The US will support the delivery of advanced fighter jets to Ukraine by allowing Western allies to supply American-made F-16s, and by training Ukrainian pilots to use the jets.
It would certainly be a military boost for Kyiv - but the devil is in the detail.
The crucial questions are: how many, how quickly, and what weapons will the jets come supplied with?
No-one doubts the ability of the F-16, which has more than proved itself in conflicts around the world.
They will be a step up from Ukraine's Soviet era Mig-29s and Su-27s, which fly comparable missions.
The F-16 radar can see further, allowing hostile aircraft to be engaged at longer ranges.
They typically come with missiles that do not require the aircraft to maintain a radar lock to hit their target - a capability that Russia currently has, but Ukraine does not.
F-16s can also launch precision bombs guided by laser, GPS, and advanced targeting systems, and are better at targeting and destroying enemy ground-based radars than Ukraine's current fighter jets.
But it is not yet clear which of these capabilities would be made available to Ukraine if the delivery of the jets goes ahead.
Training and delivery will also be a challenge for Ukraine. The computer systems on board - such as the avionics - operate in a very different way to Soviet aircraft.
In combat, pilots need to instinctively select multiple, correct modes in complex scenarios where they are at risk of being overwhelmed by rapidly developing events - a situation known as task-saturation.
Imagine as a car driver switching from a Renault to a Mercedes, and having to instantly know the position of the headlight switches, the wipers and the fog lights - all on a hugely more complicated level. It takes time and practice.
Ukrainian pilots will receive training on bespoke simulators. But it is also highly likely they would have been practising on commercially available software, which delivers a very close representation of the workflow required to operate an F-16.
Numbers are also key. It is little use sending half a dozen jets which on their own might be vulnerable to the mighty Su-35s operated by Russia.
Combat aircraft are most effective in packages where jets are grouped together for certain roles - all to carry out one specific mission.
For example, if the mission is to neutralise an enemy radar installation, you might want a "four-ship" comprising four jets to carry the missiles or the bombs to destroy that structure.
That role is called a Suppression of Enemy Air Defences (SEAD) strike. But you do not want that critical flight itself to be vulnerable to attack.
So you might have another four aircraft flying ahead in a "SEAD escort" role, armed with air-to-air weapons, to protect the SEAD strike from enemy planes.
The point is all this requires many aircraft, and they need to be supported by other assets.
That would include surveillance planes to warn about enemy fighters in the area, ground maintenance crews to ensure the upkeep of the jets and having, of course, the necessary infrastructure to take off and land safely.
So the US decision to give the OK to other nations to supply F-16s marks the start of a complicated process and much work will be required to get to delivery.