Os F-14 Tomcat are among the most powerful fighter jets in Iran. In all, 80 units were acquired during the government of Shah Reza Pahlavi, but only 79 were delivered. The last plane was stranded in the United States after the Islamic Revolution. Today, of the 79 fighters delivered, only 41 remain in service. Even with the embargo, the Iranians were able to keep some planes in service, as well as bring others back to operational status. Iran claims that some Tomcats have been upgraded to the F-14AM standard with help from Russia. However, details of the upgrade were not revealed.