The Stockholm - Arlanda airport rail link is a public-private partnership opened for traffic in 1999. This paper addresses costs and benefits of giving a private company control over one section of the otherwise public railway network. The project has reduced the pressure on the public sector's budget and reduced the need to raise efficiency distorting tax revenue. The number of passengers has been below expectations. Track capacity may, however, be sufficient to negotiate an increase the supply of rail services by way of extending existing commuter trains, in that way attracting more passengers.