An 18-year-old was critically injured when his Jeep crashed 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 tractor-trailer tried to get out of the way of 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, she said. The 18-year-old driver, from Joplin, Mo., was extricated from the smashed vehicle and flown by helicopter to Kansas University Hospital for emergency medical treatment.

The driver of the tractor-trailer, from Illinois, wasn’t injured.

The names of the drivers likely will be released Monday, Wempe said.