To show the effect of an explosion of a BUK missile and to prove DSB made incorrect conclusions Almaz Antey took an IL86 aircraft and had a BUK missile explode near it.
Almaz Antey did not invite press, independant experts nor members of the DSB lead investigation team to observe and validate the test.
Metabunk has some interesting comments about the test.
This is really strange. As the Russian Federation is accused of having delivered the BUK and likely operated the BUK, it would be logic to invite all the press to watch the test. This is quite a spectacular sight and would for sure generate a lot of attention in press.
The first time the results of the experiment were shown to the press and public was at the Almaz Antey pressconference at October 13 2015. Foreign press was invited a few days before to come over t attend the pressconference. Costs for travel and hotel were paid by Almaz Antey.
The image below shows the response of DSB to a letter of Rosaviatsiya. On the right column DSB explains why the results of the AA test were not part of the DSB investigation. The full response can be seen here.
The experiment can be seen here