Three German nationals were killed when their light aircraft crashed trying to make an emergency landing on a national highway in the remote Northern Territory.

The men died when their single engined Cessna 172 crashed on to the Stuart Highway, north of Tennant Creek, just before 11am (CST) on Saturday.

The three Germans, part of a wider group, were its only occupants.

Police believe the pilot was trying to making an emergency landing on the highway, about 20km north of Elliott, when the plane crashed.

The aircraft flipped during the crash, ending up on its roof on the northbound side of the highway, the main road between Alice Springs and Darwin.

The engine was separated from the wreckage during the smash, with debris scattered across an area up to 200 metres away.

The Cessna, which had been chartered in Western Australia, was one of three aircraft in a group en route from Katherine to Kings Creek Station.

The other two planes in the group landed at Tennant Creek with members of the party, also believed to be German nationals, interviewed by police.

The Stuart Highway was completely blocked for much of the day as emergency personnel worked to remove the wreckage.

Motorists have been warned to expect continuing delays with the northbound lane of the highway expected to remain closed at least overnight until Australian Transport Safety Bureau investigators arrive at the scene on Sunday.

Police have also advised motorists travelling from Queensland to the NT on the Stuart Highway to consider delaying their trip by 24 hours.

The Cessna 172 is known, because of its popularity and numbers, as the most successful light aircraft in history.