Concerns are escalating in South Korea over possible delays in the development of the F-35 fighter jet as this could hinder Seoul’s project to deploy 40 of the radar-evading aircraft from 2018-2021.

The U.S-led multinational F-35 development program has recently been in the media spotlight due to a set of accidents, most recently on June 23, when one of the warplanes’ engines caught fire before takeoff.

Apart from the hardware issues, the development of certain software could face delays of up to 14 months, Bloomberg reported, citing a Pentagon report. The software is crucial for operating navigation, communications and targeting systems, the report said.

Amid concerns about the possible delays in the U.S.’ costliest defense program, Seoul’s Defense Acquisition Program Administration said that it would “closely watch the situation.”

“As we haven’t bought any of the F-35 jets under development yet and will purchase them from 2018, we still have some time to watch the situation and wait for solutions to come,” a DAPA official told The Korea Herald, declining to be named.

“We don’t expect any serious problems yet … with respect to our procurement schedule.”

Earlier this year, South Korea confirmed its plan to purchase 40 F-35s with a budget of 7.4 trillion won ($7.3 billion). The F-35 was the sole candidate in Seoul’s next-generation fighter procurement project as it was the only all-stealth airplane available on the market.

Seoul plans to purchase the F-35A, which is the fighter’s Air Force variant. The F-35B is the Marine Corps’ short takeoff and vertical landing variant and the F-35C the Navy’s carrier-based version.

The latest F-35 accident took place at a Florida air base last month. The engine fire led to the grounding of the entire F-35 fleet for more than three weeks. Investigators reportedly attributed the fire to “excessive rubbing” of fan blades in a part of the Pratt & Whitney-made engine.

The June 23 accident followed an engine oil leak the same month, which led the U.S. military to inspect 104 F-35 jets that have been produced since 2006.

The series of setbacks appeared to have worsened public sentiment in the U.S. as well.

The New York Times pointed out in an editorial earlier this week that some experts proposed halting the F-35 sales until operational testing is completed in 2019. It also noted that “common sense” evaporates when it comes to big-ticket weapons, and members of Congress were being heavily lobbied by “deep-pocketed” defense contractors.

The F-35 was developed under the F-35 “Joint Strike Fighter” project launched in 2001. The project is a multinational program including the U.S. and eight foreign partners: Britain, Italy, the Netherlands, Turkey, Canada, Australia, Denmark and Norway.

By Song Sang-ho (sshluck@heraldcorp.com)