The U.S. Defense Department’s top weapons buyer is assembling a team of independent experts to study the F-35 fighter jet’s software development delays.

Frank Kendall, the Pentagon’s undersecretary of defense for acquisition, technology and logistics, was ordered to put together a group to study the issue and submit a report to Congress by March 3 as part of 2014 National Defense Authorization Act, which sets policy goals and spending targets for the fiscal year that began Oct. 1.

President Barack Obama signed the legislation into law today while vacationing with his family in Hawaii.

Air Force Lt. Gen. Christopher Bogdan, who oversees the F-35 Joint Strike Fighter, the Pentagon’s most expensive weapons acquisition program, and auditors from the Government Accountability Office, the investigative arm of Congress, have identified the aircraft’s software development “as an area of risk because of its complexity,” according to an earlier version of a report accompanying the legislation.

The F-35, which is made by Lockheed Martin Corp., requires more than 8 million lines of code, compared with about 2 million for the F-16 and less than 1 million for other fourth-generation fighter aircraft, according to Steve O’Bryan, vice president of F-35 program integration and business development at the Bethesda, Md.-based defense contractor.

O’Bryan in June said Lockheed reassigned some 200 engineers to work on the F-35’s software, many from outside the aeronautics division, with specialties in space, ship-board and sensor technology, O’Bryan said. The company also invested about $100 million to build a second laboratory where the employees work in shifts around the clock to write, test, and verify the code, he said.

By using a more limited version of the software, the Marine Corps plans to begin operational flights of the fighter jet in 2015, followed by the Air Force in 2016 and the Navy in 2019.

The full software package, known as 3F, is designed to support a suite of internal and external weapons, including the GPS-guided Joint Direct Attack Munition, laser-guided Paveway II bomb, Advanced Medium-Range Air-to-Air Missile, and infrared Sidewinder missile.

It wasn’t immediately clear how many or which experts would conduct the software study.

The Pentagon plans to spend $391 billion to develop and build 2,457 Lightning II aircraft, according to budget documents. That’s $4.5 billion, or 1.1 percent, less than a projection from last year due in part to revised labor rates. The stealthy, single-engine jet designed to replace such aircraft as the F-16, A-10, F/A-18, and AV-8B.

The legislation authorizes the department to spend $5.5 billion to buy 29 of the aircraft, including 19 for the Air Force, six for the Marine Corps and four for the Navy, according to the legislative report. The figure doesn’t include funding for research and development or spare parts.