OWLS HEAD, Maine — The pickup truck being driven across the Knox County Regional Airport Friday night — which collided with a small airplane taking off — had no beacon light as is customary.

National Transportation Safety Board safety investigator Shawn Etcher said Monday that the 1994 GMC pickup truck driven by Stephen Turner, 62, of Camden had no beacon light that would make it more visible to aircraft. Etcher said the investigation will look at whether this was required at the airport.

The crash claimed the lives of two University of Maine students and a UMaine alumnus.

Knox County Regional Airport Manager Jeffrey Northgraves said Monday that the runway lights were on when the accident happened. He said those lights automatically turn on when a pilot activates the radio in the plane.

The airport manager said, however, that the truck did not have a lighted beacon on it. He said while it technically is not required, trucks that cross the runway should have one. He said he did not know why a truck was used that had no lighted beacon on it.

The Knox County Sheriff’s Department said over the weekend that just before the runway collision, Turner assisted with putting a plane away in a hangar near the airport terminal, a practice that occurs daily.

Northgraves said pilots and vehicle drivers are supposed to communicate by radio to alert each other of their movements. Northgraves said during the weekend that it was unclear what communication occurred between the pilot and driver before the crash.

Etcher said Monday that the truck driver said he had a radio and that he heard no communication from the airplane.

Before someone is authorized to have a vehicle on the runway, the person receives training, Northgraves said.

Allison Rogers, manager of the Hancock County-Bar Harbor Airport in Trenton, said vehicles are not allowed on the runway there unless the driver has received training and the vehicle has a lighted beacon to make it visible.

Northgraves said he expects to hold a meeting soon with all users of the Knox County Regional Airport to discuss any changes needed to improve safety in the wake of the Friday evening crash.

“We will sit down with everyone inside the fence and look over our procedures and how to tighten them,” Northgraves said.

He said he can take steps on his own as airport manager to increase safety requirements. He said airports can have tighter restrictions than required by the Federal Aviation Administration but not less strict than FAA rules.

Etcher said that the man believed to be the pilot of the airplane that crashed had certification to fly both day and night and to fly with visual observations alone. Investigators say they cannot confirm the identities of the victims until DNA testing is completed by the Maine Medical Examiner’s Office.

But University of Maine officials and members of the Lambda Chi Alpha fraternity on campus over the weekend identified the three men killed in the crash as William B.J. Hannigan III, 24, of South Portland, who is believed to have been the pilot of the Cessna; David Cheney, 22, of Beverly, Mass.; and Marcelo Rugini, 24, of Muliterno, Rio Grande do Sul, Brazil. The three men were members of the fraternity and had left Bangor International Airport at 11:30 a.m. Friday for a day of flying.

About an hour before the crash, the plane flew over Spear’s Vegetable Farm in Nobleboro, which Rugini has called home since coming to the United States six years ago through a program called Communities for Agriculture.

It is not clear yet why the plane later landed at the Knox County Regional Airport. But according to investigators, the airplane was taking off on the 5,000-foot runway at that airport and had just gotten off the ground at about 4:44 p.m. Friday when it struck the front end of the truck driven by Turner.

The plane continued on, reaching an estimated altitude of 150 feet, when it banked to the left and then nose dived in the woods about 200 yards off the runway. The plane burst into flames.

Northgraves said the debris field was small.

Turner was not injured in the crash. The truck had minor front-end damage and was impounded by investigators on the evening of the crash.

Etcher said Monday that the on-site investigation would conclude Tuesday, but that the NTSB likely won’t issue a probable cause of the crash for six to 12 months.

The wreckage of the Cessna 172 single-engine plane was loaded onto a flatbed Monday morning and was to be taken to a secure storage facility in Biddeford used by the insurance carrier for the plane, Etcher said.

Jake Barbour Inc. of Owls Head was hired to remove the wreckage for the NTSB and to transport the pieces to Biddeford.

Etcher said once the investigation is completed by staff, the findings will be passed on to the NTSB members to vote on a probable cause of the fatal crash. He said a preliminary report will be issued in a few days but will include only information that is already known.

The airport has seen 16 crashes either involving planes at the airport or flying from or into the airport in the past 40 years.

The worst was the 1979 crash that killed 17 people aboard a Down East plane originating from Boston. That plane crashed in fog at night on May 30. Only one passenger survived.

The airport has undertaken several safety improvements since 1979, Northgraves said Monday.

The most important was the installation in 1995 of the instrument landing system that allows planes to land in fog and lower visibility. Equipment on the ground in the ILS system shows pilots their positions and that of the runways.

In 2008, the airport erected gates at points where vehicles could access the runways and also constructed a parallel taxiway for planes. This allows planes to get off the runway quicker upon landing and also to get on the runways just before takeoff.

The county’s plan for improvements in 2013 include a $1.2 million fence to keep deer, turkeys and other animals off the runways. Northgraves said earlier this month at a meeting of the Knox County Commissioners and Knox County Budget Committee that there had been five instances in the past year of contact between aircrafts and wildlife. He said that amount in one year was more than in all the time since he became airport manager in 2004.

The airport has two runways. One is 5,000 feet long and is used by jets and larger planes and the other is a 4,000-foot runway that is mostly used by smaller planes.

The plane that crashed Friday was using the 5,000-foot runway.

Northgraves said there is a point of no return when a plane is taking off based on its speed and the amount of runway remaining. He said in this instance, the plane struck the truck at about the 1,000-foot mark and that there was about 4,000 feet of runway left.