While I am also frustrated that many European states do not take their erga omnes obligations serious in regards to genocide, do I think shooting down a plane on the basis of a disputed warrant would not be a proportionate measure[^1].

Generally planes can be ordered to land, but if they ignore that call and there is no further threat (like many Russian planes), they will generally escort these planes until they are out of the airspace. States do this based on the prohibition of the use of force as defined in article 2 of the UN Charter.

[^1]: https://opil.ouplaw.com/display/10.1093/law:epil/9780199231690/law-9780199231690-e1138, '[T]here appears to be a measure of agreement at least insofar as a State can respond proportionally to the violation of its airspace by foreign aircraft (see Korean Air Lines Incident [1983]). However, there is an equal measure of disagreement as to the exact limits of this right. In any case, the principle of proportionality must be applied for every action taken. However, even in the light of these prerequisites, it is still highly disputed whether the downing of an aircraft constitutes a legitimate means in terms of ultima ratio'.

They are indeed tracked down by fighter jets and followed out of the airspace. My point was more that international law doesn't allow a state to just shoot stuff, even after a warning, when there is no immediate threat.