A small plane crashed on the westbound side of Route 50 near Church Road in Bowie, Md. (Mark Gail/for The Washington Post)

A small airplane crashed alongside Route 50 near Freeway Airport in Prince George’s County on Monday afternoon, seriously injuring all three people aboard, police said.

At 3:42 p.m., the single-engine, fixed-wing plane struck the tree line beside lanes of westbound traffic and landed on a shoulder of the road, police said. The aircraft experienced problems that appeared to be mechanical following takeoff, said Maryland State Police Sgt. Jon Hill.

No one on the ground was injured, but the three people aboard were, said Prince George’s Assistant Fire Chief Alicia Francis. A woman suffered life-threatening injuries, and two men suffered critical injuries, police said Monday evening.

The crash came as the three-day Labor Day weekend was drawing to a close and beach visitors were returning to the area on Route 50 from Maryland and Delaware towns.

Police said all westbound lanes of Route 50 were closed for about an hour. Traffic was snarled as the road remained partly closed for about 21 / 2 hours.

Freeway Airport, near Bowie, is in one of the more rural areas of Prince George’s, and according to its Web site, at least eight flight instructors provide pilot’s lessons.