Although note that avionics fall under the "transportation" exemption, and RoHS does not apply. That said, the supply chain has moved largely towards RoHS comp

Although note that avionics fall under the "transportation" exemption, and RoHS does not apply. That said, the supply chain has moved largely towards RoHS compliance, so some avionics inherit that for supply chain simplicity. Some don't; there's a cottage industry reballing BGAs from lead-free to leaded solder for aerospace applications.