Västerås Airport was originally established as a military airbase in 1931 to serve the Swedish Air Force's 1st Flying Corps, which later became Västmanland Wing, F1 Hässlö. Civilian flights from the airport began in 1976, with Scandinavian Airlines (SAS) operating the first route to Copenhagen. Military operations continued until the base's closure in 1983. The airbase was then taken over in November 1985 by Västerås Municipality, whose intention was to develop it into an aviation training centre. In April 1999, the Swedish Civil Aviation Administration (Luftfartsverket) expressed interest in acquiring a stake in the airport, due to increasing congestion at Stockholm Arlanda Airport. The following year Luftfartsverket purchased a 40% stake in the airport, with plans to develop passenger traffic. The objective was to increase annual passenger numbers from 120,000 to approximately 500,000 within five years. In 2001 the airport changed its name from "Västerås Airport" to "Stockholm Västerås Airport" allowing it to be included in Stockholm's STO IATA code, and to increase its appeal for international flights. This followed the example set by Stockholm Skavsta Airport in 1991. That same year, low-cost airline Ryanair commenced operations at Västerås Airport, initially offering flights to London Stansted Airport. It was later revealed that the airport had offered Ryanair discounts totaling 3.5 million SEK, in breach of municipal law. These included 50% reduced passenger fees and 67% reduced landing fees compared to those charged to SAS. By 2003, Västerås Airport was struggling financially, having reported a loss of 15 million kronor in 2002, a drop in equity from 30 million to 14 million kronor, and total debts of 111 million kronor. The municipality approved multiple rescue packages for the airport, including one of 57 million kronor in 2006. That same year, Luftfartsverket sold its 40% share back to Västerås Municipality for a nominal price of 1 kr. In response to a proposed aviation tax, Ryanair announced an end to its operations at Västerås Airport on 11th July 2006. After the September 2006 election, the new government abolished the proposed aviation tax. Ryanair returned to Västerås Airport in 2007, launching new routes to London Stansted and Dublin. TNT operated freight flights between Liege and Västerås Airport between 2008 and 2015, when the service was relocated back to Örebro. In 2009, Ryanair launched two new routes from Stockholm Västerås to Barcelona (Girona) and Weeze. The route to Weeze was discontinued after a few months due to poor profitability. In April 2010, Ryanair started another route from the airport to Alicante. In 2011, the airline expanded its summer schedule to include Malaga as a new destination and discontinued the Barcelona route. During the summer of 2012 and 2013, the destinations included Girona, Palma de Mallorca, Alicante, Malaga, London, and Antalya. In the summer of 2012, the airline Flyglinjen operated flights between Västerås and Visby. This route was terminated in 2013 . On 31 October and 1 November 2013, Ryanair began two new winter routes to Gran Canaria and Tenerife (South). However, the Gran Canaria route was prematurely terminated on 9 January 2014. On 14 December 2013, Ryanair announced that the route to Barcelona-Girona would not be operated during the summer of 2014, and the Palma de Mallorca route was also at risk of being discontinued. This was confirmed on 8 January 2014, when Ryanair published its summer schedule for 2014, which included only the destinations Alicante and Malaga. The airport played an important role during the 2014 Västmanland wildfire, serving as a base for water bombers and rescue helicopters. Between May and October 2016, the Icelandic airline Wow operated regular flights between Västerås Airport and Keflavík International Airport in Iceland. By December 2019, the only flights operating from Västerås were Ryanair flights to London Stansted.