Israel is upgrading its thirty 1970s vintage F-15 fighters so that they can use JDAM and other smart bombs, and continue flying for another decade. Israel has 107 F-15s, and all but the 30 oldest ones can already use smart bombs. This additional upgrade effort is partly in response to the growing number of delays in delivering the new F-35. Moreover, the 31 ton F-15A/B/C/D/Is that Israel uses have larger carrying capacity (up to 11 tons, compared to four tons) and range than the 350 F-16s. While the F-16s are Israel's principal combat aircraft, the larger F-15s can still defeat anything hostile neighbors have, but provides more effective service as a fighter-bomber.