NASA is opening up the International Space Station for tourists with the first mission as early as 2020.

The National Aeronautics and Space Administration is opening up a space station to tourism.

NASA plans to open the International Space Station for "private astronaut missions of up to 30 days," with the first mission as early as 2020. As Boeing and SpaceX are developing capsules to carry humans to the ISS, the agency said over the summer that the two companies will handle private tourists and any services related to them.

NASA will start with two private astronaut flights a year, with each trip lasting 30 days maximum each.

Each trip will likely cost over $50 million, with NASA getting $35,000 for each night a private astronaut spends on the International Space Station.

Companies will also be allowed to bid for new activities on the ISS, as NASA unveiled a new directive to "enable commercial manufacturing and production and allow both NASA and private astronauts to conduct new commercial activities aboard the orbiting laboratory," the agency said in a press release.

The commercialization of the ISS has long been considered a way to reduce NASA's yearly costs for operating the station. Additionally, the ISS has been touted as a stepping stone to build an ecosystem of business in orbit around the Earth, so companies can manufacture, experiment, advertise and even host tourists.

Shortly after his appointment as NASA administrator, Jim Bridenstine met with private companies about managing the space station. Although NASA has been increasing its reliance on private space companies, none of the companies working on low Earth orbit space habitats have expressed interest in taking over the ISS wholesale.

Boeing has been NASA's primary contractor on the ISS ever since the aerospace giant was selected in 1993 to develop and build the floating lab. About a third of NASA's more than $3 billion annual budget for the ISS is for operating costs, The Washington Post reported last year.