An 18-year-old was critically injured when his Jeep crashed head-on into a semitrailer early Saturday morning, the Douglas County Sheriff’s Office said.

The accident shut down a section of U.S. Highway 24-40, near the Lawrence Municipal Airport, for about six hours.

The driver of the semi told officers he couldn’t avoid hitting the westbound Jeep, which had drifted over into the eastbound lane of the highway, said Lt. Kari Wempe, a sheriff’s office spokeswoman.

There was “considerable damage to the Jeep,” Wempe said. The 18-year-old Joplin, Mo., man was extricated from the vehicle and flown in a Flight for Life helicopter to Kansas University Medical Center for emergency medical treatment.

The driver of the semi wasn’t injured.

The names of the drivers weren’t immediately available.