A snake has terrified a pilot in the Northern Territory by appearing in the cockpit of a small plane mid-flight, forcing an emergency landing.

The snake slithered out of the dashboard of an Air Frontier plane 20 minutes after take-off from Darwin Airport on Tuesday afternoon.

Pilot Braden Blennerhassett made a mayday call and swiftly grounded the plane, which was not carrying any passengers.

"Sure enough, out of the corner of my eye, I see a little bit of movement there," he said.

"Lo and behold, in between the instrument panel and the dashboard, a stow away came on board and it took me a while to register that it was actually a snake.

"I turned [the plane] around and got it headed back towards Darwin there and said 'look, you're not going to believe this. I've got snakes on a plane'," he laughed.

Mr Blennerhasset says while the air company's staff were sceptical at first, when he started requesting a snake handler back at the air field his concerns were taken seriously.

Air Frontier director Geoffrey Hunt says it is a first for the Top End.

"I have heard of crocodiles being loose in planes but not snakes," he said.

Snake catchers were called in but the reptile has not been spotted since.

Traps have been set and Mr Hunt says the plane remains grounded.

"Until we find the snake, it's not good for business," Mr Hunt said, adding that he hopes the plane will not have to be pulled apart to track it down.

"But obviously we won't be using [the plane] until we're comfortable the snake is not onboard anymore," he said.