The South Korean air force has managed to derail the selection of the Boeing F-15SE Silent Eagle for its F-X Phase 3 fighter requirement, instead pushing for the Lockheed Martin F-35 Lightning but again raising doubts about the openness of the country’s combat aircraft competitions.

The decision appears to deprive Boeing of its best chance of sustaining the F-15 production line past 2018, when the last unit is due to be completed for Saudi Arabia. The South Korean order has offered to underpin development of features that would increase the combat effectiveness of the type, making it more attractive to additional customers.

South Korea’s Defense Acquisition Program Executive Committee on Tuesday decided to restart the F-X Phase 3 competition, despite a decision in August that the F-15 was the only contender that met the F-X Phase 3 budget of 8.3 trillion won ($7.7 billion) for 60 aircraft. The losing types were the F-35 and Eurofighter Typhoon, the latter eliminated because of a bidding irregularity. A decision in the reopened competition is to be made within a year.

The air force, which industry and government officials say has always wanted the F-35 for the requirement, especially after Japan chose the type in 2011, mounted a barely veiled campaign against the F-15 after its selection. Retired air force generals, for example, criticized the decision, making public statements that serving officers could not express. Unnamed air force officers were quoted in the press saying that, with the selection of the F-15, the program was “veering onto a wrong course, contrary to original aims,” presumably the F-35.

If South Korea does eventually choose the F-35, it will be the third non-partner country, after Japan, to order the aircraft despite its cost and the risk of renewed development difficulties.

South Korea’s problem is that this is the second time in 11 years in which one of its fighter requirements appears to have been predetermined, suggesting that bidders may be wasting their marketing money in competitions that are not competitions at all. After Boeing won the F-X Phase 1 competition for 40 fighters with the F-15K in 2002, losing contender Dassault said it would not take part in future South Korean fighter competitions. The French company had evidently concluded that its bid, however attractive, could never have won.

For the F-X Phase 2 requirement for 20 fighters, no competing manufacturers took South Korea’s Defense Acquisition Program Agency seriously when it called for alternatives to the F-15. Boeing was the only bidder. In 2008 it contracted to supply 21 F-15Ks, including a replacement for one that had crashed.

The defense ministry explains the setting aside of the F-15 selection for F-X Phase 3 partly in terms of threats from North Korean nuclear arms and “asymmetric weapons.” But South Korean government officials have said that the threat on the Korean peninsula has not been a major issue in the requirement. Moreover, the North Korean threat is hardly new.

The ministry also cites rapid advances in aeronautical technology. The major new technical development among South Korea’s neighbors in recent years has been the appearance of China’s J-20 stealth fighter prototype. But that was more than two years ago, during which time the ministry did not move to call a halt to F-X Phase 3.

Defense ministry spokesman Kim Min-seok almost announced the decision of planned new competition. “There is a consensus that South Korea needs the fifth-generation fighter jet to deter the growing threat posed by North Korea,” Yonhap news quoted him as saying. Only the F-35 meets that definition.

Another difficulty for South Korea is that the F-4 Phantom and F-5 Tiger fighters that F-X Phase 3 is to replace are already of doubtful combat value. The replacements were supposed to arrive between 2017 and 2021.

“Boeing is deeply disappointed by the Republic of Korea’s Defense Acquisition Program Executive Committee decision,” says the F-15’s manufacturer. “Boeing has rigorously followed the Defense Acquisition Program Administration’s instructions throughout the entire process. We await details from DAPA on its basis for the delay while evaluating our next options.”

Lockheed Martin says it will continue to support the U.S. government in the process. The F-35 would be sold under the government’s Foreign Military Sales system.

Throughout the competition, EADS and its partners in the Eurofighter consortium always had to wonder whether they were only a stalking horse for the U.S. fighters, especially the F-35. Quite apart from the South Korean air force’s preference for the F-35, South Korea is always under diplomatic pressure to award major defense import contracts to suppliers from the U.S., whose armed forces guarantee its security.

A key question now is whether Eurofighter and Boeing will bid again, especially in view of the defense ministry’s declaration that a “fifth-generation” fighter is needed. Boeing will “explore all of its options,” says an industry source. That will presumably include whether to do more work in developing the F-15SE, which offered limited stealth, advanced avionics integration, and considerable payload-radius, as well as a moderate price in competition with the F-35.

Boeing is under contract to deliver 84 new-build F-15SAs to Saudi Arabia. Though Boeing should finish building them in 2018, the last is due for delivery in 2019. Long lead items would normally be ordered about two years before aircraft delivery, so Boeing appears to have about three years in which to drum up new F-15 business.