Fearing major delays to the Joint Strike Fighter, the IAF is exploring whether to purchase a used squadron of F-15 fighter jets from the US Air Force, as it faces a possible drop in its number of combat aircraft.Israel decided to purchase a squadron of 20 F-35 stealth fifth-generation JSFs, which are made by Lockheed Martin, last year in a massive $2.75 billion deal, to be financed by the military assistance Israel receives from the United States.RELATED:Stealth powerReported 3-year delay in F-35 program may impact deliveryThe program has recently encountered significant development delays. Other countries, such as Turkey and Norway, have also reportedly put their purchases of the aircraft on hold. The F-35 is supposed to be one of the most advanced fighter jets in the world and will enable Israel to phase out some of its older F-15 and F-16 models. According to the IAF, the plane will significantly boost Israel’s deterrence in the Middle East and provide it with an edge on adversaries that operate advanced anti-aircraft systems, since it is a stealth jet that cannot be detected by existing radars. Due to the delays, the IDF is working on a plan that includes upgrading its current fleet of legendary F-15s and F-16s that it had planned on phasing out, as well as the procurement of a squadron of used F-15s from the USAF that will serve as a “gap filler” for the IAF until the JSF arrives, now expected as late as 2018.