Pilots flying Boeing planes in recent years have reported flight-control problems they blamed on malfunctioning software -- not on the company's maligned 737 MAX jets, but widely used earlier versions of the plane that are still in the air.

Commercial pilots flying Boeing's NG, or "Next Generation," models have registered concerns on a variety of computer problems through the Aviation Safety Reporting System, a database administered by NASA.

In the past three years, pilots on different flights reported a range of issues, including losing airspeed on takeoff in some cases or the plane's nose pitching downward without their command.

Dozens of grounded Boeing 737 MAX planes crowd a parking area in Seattle. Pilots say earlier versions of the plane, which are still in the air, may have safety risks too. Credit:AP

Earlier this week, the Federal Aviation Administration disclosed that it had identified additional computer problems with the MAX, aside from the anti-stall software known as MCAS that has been linked to two fatal nose-dive crashes in recent months. Fixing the newly discovered software glitch could take as long as three months, people familiar with the matter said on Thursday.