Tessari personally participated in the attack, claiming four French Morane-Saulnier MS.406 shot down; for this action he was awarded another Silver Medal of Military Valor.

On September 24, Lieutenant Colonel Ernesto Botto was appointed Undersecretary of State for the Air Force of the Italian Social Republic, and at the end of the month he went to Rome, where he met Graziani and Tessari; the latter remaind in Rome until November, when he moved to Bassano del Grappa, being entrusted with administrative tasks within the Air Force of the RSI.

He too ended up clashing with them, however, due to their attempts to fully absorb the ANR in the Luftwaffe; in May 1944 he wrote to Mussolini that the Germans were systematically dismantling the hangars of Italian air bases in order to send the metal to Germany.

He eventually resigned from his post on 26 July 1944 (although he de facto remained in office until August 20), being replaced by Colonel Ruggero Bonomi and retiring to private life in his native Belluno.

After the end of the hostilities he was accused of collaborationism, imprisoned for eight months in the military prison of Forte Boccea in Rome, subjected to an 'epuration' process and forcibly placed on absolute leave.