Reports indicate that South Korea’s Joint Chiefs of Staff revised the F-X III operational requirements to favour the F-35, leading to the de facto private contract with Lockheed Martin. The number of fighters to be procured was decreased from 60 to 40, apparently to meet the F-35 budget proposal due to its greater cost per unit and extremely high operational costs relative to the Silent Eagle. 20 more fighters were later added. The final contract was then signed in March 2014. Charles Park, a researching member of the Defence Management Research Institute affiliated with Kookmin University in Seoul, stated regarding the mysterious revision of the DAPA’s decision: “The F-X III selection process is a black mark on DAPA’s procurement records… No one can deny the F-35 has better stealth capabilities than the F-15 Silent Eagle. But the Silent Eagle won the race fairly under due rules. Nevertheless, the DAPA did a flip flop on its decision without warrant.”
While the F-35 has marginally superior stealth, the F-15 surpasses it in all other capabilities and in all roles - with the former having been designed as a light support fighter and the latter having been designed as a specialised and highly elite frontline platform. This is reflected in the F-15’s armaments, manoeuvrability, speed, operational altitude, sortie rate and its ability to function independently - all of which are beyond comparison with the capabilities of the F-35. Despite its superior stealth, the F-35 is the slowest modern combat aircraft in the world and one of the lowest flying, whereas the F-15 remans the world's fastest fighter and can operate at extremely high altitudes - which is set to more than make up for its inferior stealth capabilities in terms of survivability. In highly contested combat zones such as the Korean Peninsula, where threats from enemy fighters and surface to air missiles are manifold, the F-15SE thus appears a far more valuable fighter.
Another advantage of the F-15 is that it is a tried and tested design - unlike the F-35 which even the United States military has a great deal of trouble operating in peacetime due to is poor reliability. While the F-15 is widely held up as perhaps the most capable Western fighter ever designed (if not second only to the F-22), one of the most successful platforms in the history of U.S. military aviation, the F-35 has by contrast received a great deal of criticism from the U.S. government, various think thanks and a number of the platform's export clients. PGO, NSN, Rand Corporation and the Senate Armed Services Committee have been among the fighter's staunchest critics - as have numerous high ranking members of the U.S. military including the Pentagon's Chief weapons tester Michael Gilmore. Senate Armed Services Committee Chairman Sen. John McCain referred to the F-35 as "both a scandal and a tragedy with respect to cost, schedule and performance." Issues have included software failures, extreme maintenance requirements and design flaws seriously compromising combat capabilities among numerous other severe shortcomings.
The commissioning of the F-15SE, much like the F-15K before it, was set to bring considerable benefits to South Korea’s defence industry due to joint production with Seoul and the incorporation of indigenous components. 40% of the F-15K was manufactured in South Korea, and 25% of the fighter was assembled there. A similar agreement for the F-15SE would have amounted to billions of dollars in contracts for Korean producers, where the F-35A by contrast is manufactured almost entirely by NATO member states and Japan and will provide negligible benefits for Korean producers.
Ultimately with South Korea’s former President Park deposed and recently given an extended prison sentence for corruption, the possibility remains significant for other officials to be similarly indicted based on military acquisitional choices made under her administration. With the F-15SE program terminated by Boeing and F-35 deliveries having already begun, a return to the original contract remains unlikely. The effect will be the serious undermining of South Korea’s aerial warfare capabilities. With North Korea having shown interest in acquiring the Russian Su-35, a fighter already fielded by China, and with Japan fielding its own elite F-15J heavy fighters and set to induct a new elite air superiority fighter in the near future, the F-35 will be far less capable of engaging the elite heavy platforms of Korea's neighbours than the F-15SE would have. Seoul will likely have to rely on its older F-15K to counter enemy air superiority fighters if needed, a role for which the F-35 is highly unsuitable. While reverting to the original contact with Boeing is all but impossible now, with funds having already been transferred to Lockheed Martin and the F-15SE program having been cancelled, reduction in the number of F-35 fighters on order, particularly given both ongoing performance shortcomings and Seoul’s detente with Pyongyang, remains a possibility.