Why are Russia and China not upgrading Iran’s Air Force ?
There are many misunderstandings about the China-Iran arms trade. Any trade is a bilateral will, not a unilateral will.
I provide some basic information:
1. Sanctions.
China is a member of the P5 and will inevitably support and abide by the resolutions adopted by the UN Security Council.
So far, most of the UN Security Council's sanctions against Iran have expired, and some clauses will expire in October 2025.
The United States and other Western countries have launched unilateral sanctions against Iran.
In March 2025, China, Russia and Iran met in Beijing, and the joint statement of the three countries clearly opposed these illegal unilateral sanctions.
So. At present, there are no legal obstacles to arms trade between China and Iran.
2. Diplomatic relations.
When China engages in foreign arms trade, in addition to complying with the international arms trade rules that the Chinese government publicly declares to comply with, it is also related to the level of diplomatic relations between China and the target country. That is, the higher the level of diplomatic relations, the richer the choice in China's foreign trade arsenal. Some countries can even obtain very sensitive weapons.
China-Iran diplomatic relations are "comprehensive strategic partnership", which is at the third level of China's diplomatic relations. Saudi Arabia, Brazil, Italy, France, etc. are at the same level of diplomatic relations. In layman's terms, the weapons that Saudi Arabia can buy from China, Iran can completely copy the order. ------Except for the DF series missiles. They are orders before China publicly declared compliance with the MTCR.
China-Pakistan relations are an "all-weather strategic cooperative partnership" and belong to the second level of China's diplomatic relations. Therefore, Pakistan will have a wider range of choices in China's foreign trade arsenal. (Some countries use this relationship to indirectly obtain Chinese weapons and technology through Pakistan.)
China's J-10CE, J-35, L-15 and other fighters are all within the scope of purchase for the Iranian Air Force.
As for whether Iran is willing to purchase these Chinese weapon systems, this is not a question I can know.