The revelations about KAI's relationship with Cohen came after Michael Avenatti, the lawyer for a porn star suing Cohen and Trump, released documents that said Essential Consultants received hundreds of thousands of dollars from individuals and companies.
Telecom giant AT&T and Swiss pharmaceutical firm Novartis have also acknowledged paying Cohen's firm for consulting services meant to give an insight into Trump's approach to policy.
The Korean defense company, partnered with Lockheed Martin to build the T-50A trainer jet in hopes of securing a U.S. Air Force contract worth roughly $16 billion.
Lockheed Martin, the Pentagon's top weapons supplier, entered the T-50A into the bidding contest. The plane is a version of KAI's T-50, which is used in South Korea as well as several other U.S. partner nations.
Lockheed told CNBC in a statement, "We had no knowledge of a business relationship between Korea Aerospace Industries and Mr. Cohen, and are not aware of any connection that it may have to the U.S. Air Force Advanced Pilot Training competition."
The companies are widely expected to win the lucrative contract for the delivery of 350 aircraft.
Meanwhile, Boeing partnered with Swedish aerospace firm Saab to develop a brand-new design.
The T-X trainer program award, the Air Force's largest ongoing aircraft competition, is expected to be announced later this year.
The trainer aircraft will replace the Air Force's aging T-38 trainers that have been in the U.S. military's portfolio since the 1960s.