Brazil has bought eleven F-5 fighters from Jordan, and is upgrading them to match the capabilities of the refurbished F-5s they already have. The F-5s is a 12 ton fighter roughly similar to the MiG-21. The F-5 is normally armed with two 20mm cannon, and three tons of missiles and bombs. The upgraded Brazilian aircraft is called the F-5EM and has modern electronics, making it capable to using long range air-to-air missile (the Israeli radar guided Derby, in addition to the heat-seeking Derby). A look-and-shoot helmet is also part of the upgrade. There is only one 20mm cannon, but lots of missiles and smart bombs.
This type of refurbishment has been popular with older aircraft, as it turns an aging airplace into one that can fight at long range, and is able to take on much more recent warplanes. Brazil bought 42 F-5Bs in 1975 and 22 F-5Es in 1988. Starting six years ago, 34 of the 46 surviving aircraft were upgraded to F-5EMs, which are good for at least another decade of service. Brazil was so satisfied with the way this turned out, that they expanded the program to the Jordanian F-5s they got cheap on the second-hand market.