F - X fighter program The F - X fighter program is a phased procurement program for fighter aircraft for the Republic of Korea Air Force . F - X Phase 1 . The first phase of the F - X program was started in 2002 and resulted in the procurement for ROKAF of the F - 15K Slam Eagle . Four designs were reviewed the Dassault Rafale , Eurofighter Typhoon , Sukhoi Su - 35 and the F - 15K . , F - X Phase 2 . For the second phase of the F - X program , ROKAF has purchased 21 additional F - 15K to compensate for the retirement of their F - 5A / B in August 2007 . The avionics configuration for the Phase 1 and 2 F - 15K remains largely identical , and the only differences are that the weapon compatibility has been increased ( Bunker Busters , etc . ) and that the engines have been switched from the F110 - STW - 129A to the F100 - PW - 229EEP , an improved version of the F100 - PW - 229 . The new engines have commonality with the F100 - PW - 229 engines on the KF - 16 and are compatible with each other , allowing ROKAF the option to interchange the engines among the KF - 16 and Phase 2 F - 15K . This allows the F - 15K to be equipped with a KF - 16 ' s F100 - PW - 229 if necessary . F - X Phase 3 . The third phase of the F - X project is a bid for an advanced multi - role strike fighter aircraft by 2014 , intended to replace the aging F - 4 Phantom II and F - 5 . The rumored purchase number is 40 - 60 aircraft ( 9 billion dollar project ) . The Korean Ministry of Defense had shown interest in the F - 22 Raptor , but the United States Department of Defense did not permit the export of this advanced stealth fighter . The only candidates remaining are the F - 35 Lightning II Joint Strike Fighter , the Eurofighter , and the Boeing F - 15SE Silent Eagle . The Sukhoi PAK FA had been shortlisted by DAPA previously , but Sukhoi failed to enter the bidding competition . Saab attended the RFP meeting , but didn ' t bid its Saab JAS 39 Gripen . DAPA had set the date of June 18 , 2012 for the receipt of proposals with testing and evaluation taking place until September 2012 and with a winner due to be announced in October 2012 . However , both Lockheed and EADS failed to submit Korean versions of their pricing and technology transfer details , leaving Boeing as the only vendor to meet the requirement for their proposal . The proposal deadline was extended to July 5 . The RoK defense establishment had been resisting calls to delay the decision until after the presidential election . The decision to purchase 60 fighters is now due to be made by mid - 2013 . Emphasis is being put on driving down costs , offsets , and technology transfer . Sources in South Korea say part of the focus of which aircraft to select is being heavily based on technology transfer for the indigenous KF - X aircraft program . The Department of Defense formally notified the U . S . Congress of potential sales of the F - 35A Lightning II and F - 15SE Silent Eagle on 29 March 2013 . Lockheed was pleased that the formal Congressional notification process was under way , but noted that price discussions are " on - going . " Boeing feels that the F - 15SE is a better bid , as it is cheaper and offers commonality with current F - 15K Slam Eagles . However , Boeing ' s bid is more complicated because it is both a direct commercial sale and government - to - government foreign military sale . The Eurofighter Typhoon is still an option , but it is likely that South Korea will choose to purchase American aircraft , as they have previously . In response , EADS has offered to manufacture 48 out of 60 Eurofighter Typhoon Tranche 3 fighters domestically in South Korea . Senior South Korean government officials claim that the F - X Phase 3 competition is not aimed at defending against or striking North Korea , but for keeping pace with the fighter developments of its neighbors . With Japan ' s decision to buy the Lockheed F - 35A , China ' s development of the Chengdu J - 20 , and Russia ' s work on the Sukhoi PAK FA , South Korea is in need of upgrading its fighter technology . The bidding was extended because all three initial bids were above the $ 7 . 3 billion limit for the 60 aircraft ( i . e . more than $ 121 million per aircraft ) . During bidding sessions from June 18 to July 5 , Boeing , Lockheed , and EADS submitted 55 separate price proposals . On 10 July 2013 , DAPA temporarily suspended bidding , as they were experiencing difficulties in making the companies offer prices within the estimated budget . According to multiple sources , Lockheed did not submit either a fixed price or a maximum price during the bidding process . On 25 July 2013 , DAPA announced bidding would resume in " the third week of August . " Analysts had said that was unlikely to close the price gap that stalled the previous bids , so DAPA is considering various options , including reviewing the project , increasing the overall budget , or even a split buy . Bidding will resume from August 12 – 16 and has a required price of $ 7 . 45 billion . The Lockheed F - 35 may face an early exit because it can not be guaranteed a fixed price . Since it is still in development , price may go up significantly and exceed the limit . Lockheed might sharply push down costs in the new round of the bidding to win the deal . The runner - up or a third place aircraft has a chance to secure a deal if either of comes to within the given budget . The F - 35 may only have a chance if DAPA calls off bidding and increases the budget for the program . On the final day of bidding , the F - 15SE and Eurofighter Typhoon came within the given budget . DAPA admitted at least one fighter satisfied the procurement price , but declined to announce how many aircraft closed the price gap citing the ongoing procedure . As there were companies that offered price within budget , they will proceed to the next step . DAPA will evaluate all three fighters before a committee meeting and pick a winner by September . Any aircraft that exceeds the budget will not be signed for the contract . There is the possibility that there will be no winner . After Boeing reduced their bid on the F - 15SE and the other two were disqualified , the F - 15SE appeared to have won the competition , but this will not be confirmed until mid - September 2013 . EADS maintains that the Eurofighter remains in the race and Lockheed said they had not received any official notification regarding bidding results , although sources said the F - 35 ' s bid was over - budget . Boeing also says they have not received any official notification from the Republic of Korea regarding a decision . Some South Korean Air Force officials are still pushing for an F - 35 order to use for technology transfer for its KF - X domestic fighter program . Others say focusing on acquiring an expensive stealth fighter mainly for technology use stalls the intention of the F - X Phase 3 program to replace the aging F - 4s and F - 5s . In September 2013 , DAPA said they would recommend buying the F - 15SE . Ex - Air Force chiefs had insisted that a stealth plane should be chosen regardless of price . Officials did not want to lengthen the long - delayed project and expect that a radar that can detect stealth aircraft will be developed in a few years . On 24 September 2013 , the defense ministry rejected the award and said a new competition would be held to " secure military capability in line with recent aviation technology developments . " The more advanced aircraft would allow for preemptive strikes against North Korea ' s nuclear capability and would also better match the fifth generation fighters of Japan and China . As the Phase 3 project restarted , consideration was given to a split buy with only 20 to 40 stealth fighters , or a smaller initial buy with options to pay for the full force later . Boeing consultant Ronald Fogleman has suggested a split buy of his company ' s F - 15SE and later the F - 35A to meet South Korea ' s near - term and longer - term capabilities . Just buying the F - 35A would leave it not fully capable until its software is updated to Block 3F standard in the early 2020s . This would reduce the strength of the South Korean Air Force after 2016 when F - 4s and F - 5s begin to be retired . Buying F - 15SE fighters in the near - term can deliver proven payload carrying abilities until the F - 35A software enhances its performance and weapons load . Lockheed responded that F - 35s would be fully combat capable by the time they are delivered to Korea in 2017 .